Just wanted to report that the assembly went fine - it was actually very sweet. First of all, it was only for the kids being honored; about 20 per grade. There was a speech by a former student who is now a teacher that was a little heavy on the "doing what's right rather than what's easy" rhetoric. Parents were allowed to go up and say something to their kids - I wasn't sure how DS would feel about it but I went and stood in line and caught his eye and he made signs to me that it was OK for me to talk as long as I didn't cry (the first mother up there was sobbing.)
I basically went up to soften the extremely high expectations this event set, and made a general statement to all the kids that the reason they were there was that they put in the hard work and were willing to ask for help if they needed it, and that I was more proud that they worked hard than I was of anything else.
DS said I didn't sound "too stupid." God bless the child. I am very, very grateful to be this kid's mother.