It will be a great trip, I'm sure, as long as y'all start slowly and don't try to get across too quickly. It sounds like that is the plan!

I second what everyone has said about bike safety. You will undoubtedly be on some busy roads, and you will encounter several drivers (and several dogs) that don't want you on the road. Be prepared for that.

Also, even though many people have said it, GET A HELMET AND WEAR IT. The helmet is the most important piece of gear for you to buy--more important than your shorts, your sunglasses, your jerseys, your gloves, or anything else. You shouldn't turn a single pedal stroke without first putting on your helmet, and you shouldn't let anyone in the group you're leading do so, either.

Have fun! Be safe!