What were songs you played when you were in band that you loved? Why not try those? Instead of something to challenge yourself, just play a few songs you really loved and share it with the kids. Maybe have several song choices and let them pick ones to play?

If it's a spring or winter concert, try something new, like having the band play the soundtrack to a movie/show that's playing, or something that could get audience involved. Regardless of how kids feel about their music, when they see the crowd getting worked up they'll remember that more than the music.

You should also record your first run-through with your songs and listen to it at the end of the year to see the difference yourself.

I'm also willing to bet these kids are acting funky because it's May. No matter what your school schedule is, they've got friends and family graduating and making summer plans and they're most likely daydreaming about that.