Bus thoughts: make sure the parking is available (either in their lot or on street) for the bus. Buses are large and can be a challenge for parking. Unless the parking area for a shop is large, many don't want buses taking up the few spots they have. Add in the driver's tip (yes, you have to tip them) when figuring your price for the trip. Make sure bus has a bathroom (even though most won't use it...it WILL come in handy for some). If you need help filling the bus, open the trip up to local guilds. Post info at the LQS. Try to keep the trip to reasonable time frame, as many people tire easily and don't want long, long days (even if it is to quilt shops!). See if you can rent a "handicapped" accessible (front stairs lower to ground level) bus for those of us who have trouble climbing stairs. Have a cancellation policy: full refund if cancelled in X days before the trip, 1/2 refund if cancelled 2 weeks prior, no refund if no show. (Of course, use your discretion here. You know your members...)
Lunch: Either choose a restaurant (or two) and notify them that you will be bringing a group of "X #" of people at such and such a day and time (in other words make a reservation). You probably would also want to notify them that you will need "separate checks" for the entire party (I've never gone on a quilt hop where group check is done). Best idea I believe is to have people bring their own lunch/snacks - cheaper in the long run, so more money (and time) to spend at the quilt shops! Do check with the bus company if they allow eating/drinking on the bus, though.
Entertainment: Buses nowadays, have DVD players (driver controls it), so bring along different quilt show/tutorial DVD's. (Ask members to lend them).
Participating shops: Definitely give them a "head's up" on the date/approximate time you will be visiting and how many people will be there. Many shops will give discounts/goody bags/snacks if they know ahead of time. Many will even advertise the hop for you (you may get more participants this way).
Lastly, enjoy, enjoy, enjoy!
Hope this helps.