Having done some long bus rides as both a mentor and a student on the team i would tend to agree with David on this one. Although the other question is how full is the bus going to be? If it is very full you won't have to worry about much, just spread you chaperone's around through the bus and you shouldn't see many problems. I think you should ask the students to bring entertainment/ movies but also keep some mad libs in your bag. For me and long bus rides go i normally just try to survive
. Overall i have found that if you treat kids with respect and give them their freedom you won't have to worry about bad things happening.