Van, I worked with a high school band trumpet section for a couple of years and I worked on very basic stuff. Of course, this was due to the fact that this particular section was really only capable of doing very basic stuff!
I'll echo what diz said about warm-ups. Some of these kids has such thin, unfocused sounds, that I stressed long tones during warm-ups. I also did a lot of basic articulation things with them because I have the belief that in order to articulate correctly, you air has to be moving correctly and improvement in air flow can sometimes be vastly improved with simple things in a warm up such as long tones and tounging exercises.
From there it was just a matter of working with them to get the music under their fingers which meant working on sections of the music in small bites, slowly at first, building up to performance speed and beyond, and just repeating the heck out of everything. There is something to be said for repetition in rehearsal and practice for kids at that level.
I think that you will be a great addition to this band camp and that you will do just fine. Good luck with it!