I agree that you should do the ride... and also that you should have the LBS show ya how to change a flat... that being said, should you have probs... it's an organized ride right? That means SAG support... and assuming the bike community does what it should, and you flat, most everyone who passes will ask if you're OK and if not, they'll stop and help! I have changed flats for people on 4 different rides... and twice it was for MEN Ah... it does a soul good...

have a great time