IM Dreams and Reality

I say go for it. Finishing any distance triathlon is the sum of the whole training. You can and will miss some workouts. You can make some of the missed workouts up, but some you will just have to let go. If you have been doing tris for some time, you know your body and what you can do. Trust yourself and the training plan and you will be fine.

And, don't forget to spend time with the family, too. IM is not everything

how strong is your swim?  if you are strong in the swim you can afford a bit less pool time.   is your travel by car that you could always bring your bike & trainer with you?

i don't know if you can afford coaching, but it would be ideal to have one-on-one coaching so you could tell your coach each week what your availability was and have the coach be able to maximize each workout to get you in the best position to achieve your goals.  IM training takes consistency above all else IMO.  So you would need to be extremely disciplined in using the time you do have available.  I had many many many 5am workouts.

Swing for the fence man!  Life is short and we aren't getting any younger!

~Mike

If you're constrained by a lot of travel, a coach is probably one of the best investments you can make.  He/she can help identify a training plan and likely results specific to your situation.  One of the worst things you can do is sign up for a plan that doesn't fit your lifestyle and then stress over the training you aren't getting done (or changing it up willy-nilly). 

You can probably work towards a 14-15 hour finish on as little as 7 hours per week (average, you'll have longer weeks at peak volume). 

I can relate to where you're coming from.   I'm younger but had the same thoughts, if not now then it won't get any easier.  Looking at starting our family this year, and I knew things would be tougher later.  I also travel, but luckily it has scaled back as I've started training.  I'm about half way through my program, with some good volume behind me but the heaviest just ahead.  I'm basically following the beginner ironman plan from this site.  The key things I've learned so far are:

1) Sit down every Sunday night with that week's schedule.  Write out all your travel, meetings, and personal commitments on the schedule.  Do your best to stick to the number of workouts, but most importantly, schedule your quality workouts around your travel.  Be realistic about how much energy you'll have for a morning swim if you're getting back from a trip at midnight the night before.  Thinking practically and finding the biggest holes of time where I'm most likely to be rested is always the starting point for where I slot my workouts.

2) Make sure the family understands just how much time and energy this will take.  My wife was also on-board at the beginning, but she's starting to fatigue as I get deeper into the program.  I'm up four days a week at 4:45 for the pool, straight to work, home around 6:30, then bike or run for an hour to two hours during the week.  On the weekends, I try to knock out my long work earlier so we can still have some time.  But needless to say, the impact on "quality time" with your significant other is massive, and 20 weeks is a long haul. 

3) While there is more to life than work and training, think carefully about the timing of vacation or family coming to visit.  I've got a five day vacation coming up from Wednesday through Sunday, and come back to work to travel the following Monday through Wednesday.  8 solid days right in the peak of my training without access to my normal training facilities.  I also had my family come visit for an entire week a few weeks back, and it was tough to work, train, and entertain.  Something has to give. 

4) When you travel, make sure to think about how and where you're going to eat.  I can travel and use the treadmill or exercise bike, but I hate it when I'm stuck at an airport and all there is around is a Taco Bell and a McDonalds.  I cave every time.  The travel makes sticking to a nutrition plan much more challenging.

Other than those challenges, I'm loving my training, and wish I could commit more to it. 

My only tip as you start your long road is that when you have to compromise on the fly (and you will, life gets in the way) don't choose to compromise your sleep.  Treat it as your most important discipline - you have to get your long sleep in every night.  Better to can a short run if it means you still get your 8 hours.

If you don't you will eventually break.  It's a tough road but more than possible if you don't ignore the 'silent disciplines' - sleep, nutrition and consistency. Get those three right and you'll be far more confident when you're standing on the starting beach wondering what lies ahead.

Good luck!