good idea, bad idea - re: bike

Not sure of the grade or if you have head wind or tail wind, but if you are worried about having enough energy for the way back, I would go slower on the way out.  Also, does a hour cover if you have a flat tire?  It might be better to have someone drive you there with your bike and go for a 23 miler on the way home, vs two 11.5s.  

from driving there (different route - I take freeways when driving), it's very slightly downhill on the way there (at least I know the first 5 miles are).  Which is actually what scares me about coming back!

I do have a flat kit on my bike, and it's not absolutely necessary that I'm there (not leading it or anything - and it is a recurring meeting), so if I get a flat, it's not the end of the world...

1. Don't spend yourself on the way there
2. Make sure to have enough to eat when you arrive AND before you go home, basically account for the riding plus your activities of the day in general
3. Stash an extra energy gel or bar for the ride home, just in case.
4. Bring money
5. If you're getting pooped, slow down! 

Why don't you just ride the bike route in the car prior to the meeting?  That way you have a chance to get familiar with the route.  I don't know if this is necessary or not, but if its a high traffic route it would help.

Fitness wise, I don't think you should have a problem. 

But if you honestly are not familiar with the roads you would be riding on with your bike, to the point you feel like you need a map and a GPS, then I would strongly consider at least driving the route you would be biking first.

Just because there is a road on a map, it doesn't mean it's safe for biking.  Some roads have narrow or no shoulders, low visibility, huge potholes, etc.  There are some parts of town you do not want to be on the side of the road chaning a flat.  If I'm riding through a busy area, I almost never take the shortest route.  I take the most bike friendly route.  I avoid busy intersections...especially if there is a stop sign or red light on a hill.  Makes for clipping back in very interesting.

Give yourself a little extra time and get out there and do it!

ok more seriously I am a big planner but if you have driven the route you would bike and if you are prepared otherwise in case lost (map/gps etc) and could take care of the normal emergency repair issues like flats etc - you should be ok!

Take a cell phone and have someone out there to pick you up if needed.

But you won't need it.  Take food and go easy if you get slow.  As long as you don't totally spend yourself, you will recover and be able to continue on.