i would let him stay till 10pm. being it's a school sponsored thing with chaperones, on weekends that's not an unreasonable time for a special occasion. about the ticket, i might have him or you purchase it, like in the good old days when i was growing up.
oh good GinaH, now remember when you pick him up wait in the parking lot in the car! Don't make a fuss over him in front of the other guys, and wait for the info don't pry or he'll never tell you. make him wear what he want's because chances are they have discussed this already, and if your going to kiss him goodbye don't wear lipstick and don't do it in front of the other kids. i feel for you, i have boys and i know it's hard letting go because you probably feel the way i do. This is it, i will now only see him at christmas and maybe my birthday. boo hoo I know.