you guys are overcomplicating it.
I don't think ableton does OMF's and while they are REALLY convenient for a few pieces of software you get some that don't support it, and then the BS with protools where you have to PAY a buttload of cash to get OMF support. I would say the best way is:
Here's what you do.
In ableton just set it to bounce as you would normally (the entire track selected from bar 1 to the end (don't change this or it will get confusing)...
then...
Solo each track..bounce...solo the next.. bounce...just changing the filename to suit what track you are bouncing. with the bounce always starting from the same point.
This will make it so all they have to do no matter what program they use is just import all of the wavs. Everything is lined up, ready to go allready, so there is no need to spend time figuring out how much silence to add here and there (which is not that accurate anyway because in order to keep your phase from differing from the mix you would have to figure it out on a sample level..min and sec would not be nearly close enough unless you want all their tracks to be horribly out of phase) That's what I do between ableton and logic all the time for the purpose of studio vs. live performance. (also you might want to go into a wave editing program and take tracks that are supposed to be mono and make them mono, just to save some space and CPU)