I know there's no guarantee I'll finish first IM, but what would your tips be to prevent disaster?

Training - do the work so by the time you are at the swim start you can be 100% confident that you can complete the distance. Also make sure you can handle the challenges; for instance: be able to OWS and be comfortable swimming surrounded by people, be able to ride in crowded roads while respecting the race rules (i.e. no drafting), etc.

Preparation - Make sure your equipment is 100% ready for the race. Have a plan that will guide you through the race considering the good and the bad scenarios.

Pacing - make sure you race at the correct intensity given your fitness level

Execution - Don't do anything crazy on race day (new outfit, ignore pacing, new nutrition, etc.); for any testing use your training. Make sure you can handle any curve balls during the race (i.e. changing a flat, adjusting your fit, handle on course nutrition, etc.)

Nutrition - make sure to fuel enough to complete the race but do NOT over do it and if possible KISS it. Most IM athletes struggle because they ate/drank more of what they should have. Remember, it is ok to be a bit dehydrated and fuel depleted at the end.

Have fun and smile a lot – that will make the experience much more rewarding and it will help you make a tad easier to overcome the unavoidable rough times that you’ll face at different points in the race.

It is my belief that most of the nutrition issues are caused by too much intake rather than too little. It is much easier to "catch up" if you get behind on nutrition, so I try to err on the side of eating less.

14:50 isn't a bad time.  You have over 2 hours of "contingency" time and you can train towards a faster finish (depending on when the race is). 

Far more athletes never make it to the start line, or show up injured/burned out than drop out of the race.  (Seriously, about 90-95% of the people who start the race, finish it.  And that includes the pro's who quit for season strategies. ) 

Tip 1:  Have a plan.  (You don't say how you get to the finish line in 14:50. ) 

Tip 2:  Slow down if you need to, but otherwise, stick to the plan. 

If the swim takes you 5 minutes longer than your plan, SO WHAT?  Let those 5 minutes go...I'd say the majority of blow-ups occur because people try to get this time back, so they push a little harder on the bike.  Part of the problem is they try to pick up 5 minutes off their "ideal race" time, not their "actual conditions" time. 

Tip 3:  Remain calm.  You've got a plan to get to the finish line with time to spare.  If you have some mechanical problem on the bike, be calm, take your time and calmly fix it (or wait for tech support to help fix it).  Let those few minutes go too.  Every stroke, every step puts you closer to your goal, even if it isn't as fast as you dream about.  GI problems on the run?  Go ahead and spend a few minutes in the port-o-let (unless it's 16:30 and you're still 2 miles from the finish).  In fact, maybe plan for a late pit stop (somewhere around 23 miles) to freshen up and be ready for the adoring crowds in the last 3 miles.  (You don't want to look "pained" in your finish-line pics, do you? ) 

Go and read all the wonderful race reports on this site.  You will notice that most of the folks who had tough IMs had one or more of these issues:

1.  Poor training volume.  Injuries, work, family, motivation.

2. Went out hard on the bike. 

3. Screwed up their nutrition.  This one can go hand and hand with #2.

My advice would be:

1. Get the training in.  There is no short cut.

2. Do what ever it takes to not "eat the paste" on the bike. 

3. Practice biking and running while chowing down.  Know the signs of to much water or food and not enough water or food.

#1:  Stay healthy.

And part of that is:  Don't be afraid of the taper.  Every strained muscle or inflamed tendon you bring along with you on race morning will proclaim itself to you very loudly on the run (which will quickly become a walk), no matter how you pace the bike.  Use your taper...get some rest.  Be wary of pushing through injuries late in training--there's a point of diminishing returns (starting eight weeks from race day, IMO...others would disagree, I'm sure) where the gains from training get smaller vs. the amount of time left to heal up from an injury from overuse (or accident, as happened to me, three weeks before my IM).

Other than that, it sounds like you've got a good handle on things (and, IMO, your 4:29 marathon is a sign of very appropriate run fitness, which is lacking for a lot of folks going in).

• Do plenty of biking. 100 miles should feel like an "easy" day in the saddle.
• Practice your nutrition. Know what works and what doesn't.
• Get to the START line in one piece. Harder than it sounds.
• Open water swims. Plenty of them.

Know your body. If you start to feel something weird or unusual during the day, know how to handle yourself and what you might need in order to turn the day around. Food. Water. Some sort of blister thing... know yourself and know what you need.

Don't follow the maniacs who will race like bats out of hell for the first 45 miles of the bike... Start off conservatively and see how you feel... then go from there.

MOST OF ALL: Enjoy the ride. It's a process. You will have highs and lows and douts and times when you are absolutely certain of yourself. Enjoy it all. And enjoy race day... because it's the CELEBRATION and CULMINATION of a summer's worth of hard work.

Which IM are you doing?

Edited to Add: I just read some of the other responses... I broke my pinkie toe 5 weeks out from IMWI last year... I had to "run" the marathon with the side of my shoe cut out, because the toe did not heal in 5 weeks and was swollen and painful with every step, but there was no way I was going to let that stop me. Be ready to HTFU.

Also, for me, at least, in my final huge weeks of training... I was not thinking clearly. I was exhausted and sore and stiff and just "out of it". It was in this time period that I ran into my boyfriend's parked car, broke my toe, and had a little meltdown @ the lake.

Make sure you get enough sleep.  

I was in the same boat as you - first IM w/ 2 little kids. It can be done!  One thing I learned is to trust your training. I used Gale's plan and always worried that other people were training longer/harder/differently than I. Stick to the plan, be consistent about your training and race day, trust it. Trust your body to do it's stuff - put in the training time and enjoy race day.  Don't get discouraged if you miss a workout or two - or if you have a complete emotional meltdown at some point during training. Been there and you get thru it. Practice your nutrition, pacing, clothing, etc. before race day. Oh, and after the race, there's nothing wrong with having your kids refer to you as "Ironmommy"

You already have lot's of good advice.  Here are my comments.

1. It's all about the bike.  If you make the bike cut off you can almost walk the entire marathon and finish if you have to. 
2. I know you've read it before, but DON'T try anything new on race day.   I made that mistake in 2007.
3. Practice nutrition and follow your plan.  I still haven't figured out my proper nutrition even after completing 2 IM's. 
4. On race day remember, Slow is Smooth; Smooth is Fast.
5. Have fun and enjoy the training and the overall IM experience.   Race day is just a stunt.  Training for an IM is where you earn the title of Ironman. 

Fixed it for you Mike. 

Great advice has been given, so I will keep it simple.

Stay healthy.  Log the training.  Execute your race plan (pacing, nutrition, etc).

I did IMFL with two little boys in tow and working full time - it can be done!

Good luck, see you in Ohio!

Fixing the collarbone came after the race. 

That definitely changed my race strategy though.  At that point, it was slow down and get through the day.  Nutrition?  Out the window.  Pre-race goals?  Tossed aside. 

Thanks Captn. 

The below link is from a TriFuel article from Dec 2007 and I found it helpful to read and made it my mantra at my IM.  I practiced my pacing strategy at a HIM 8 weeks out from the full and knew what to expect. 

"Don't Eat the Paste"

http://www.trifuel.com/training/triathlon-training/the-endurance-nation-four-keys-to-ironman-execution

Hope you find some useful info that will help you achieve your goal.

x2