It would be great if you had an "out" if you needed it, as BigBlueToe suggested. If that were the case I'd say don't think twice - just do it. If you do decide to go, don't make the same mistakes my non-riding friends usually make:

- Check the tire pressure before embarking
- Oil the chain if needed
- Check overall condition and adjustment of the bike
- Check your fit on the bike
- Bring a pump and patch kit, or at least be sure your friends have that, assuming they won't leave you
- Bring plenty of water
- Bring something to snack on along the way
- Have a good breakfast before going - my favorite is pancakes and eggs

It's good that the route is flat, however if you run into headwinds it will still be tough. Personally I'd rather ride up a hill than into a stiff breeze.