Oh, I feel your pain. Obviously, the problem here is, WHY ARE THEY ONLY GETTING 30 MINUTES FOR LUNCH??!!
Don't count on those kids getting 25 minutes to chit-chat, either. In my DD's school, the first ten minutes of lunch was getting the kids to line up and be quiet, march to the lunch room, stand in line again for lunch (even for kids who brought their lunches), and then sitting in assigned seats, which weren't necessarily next to their friends (definitely not, in DD's case). DD regularly came home with her lunch half-eaten, because there was too much time taken up by teacher tomfoolery.
Our kids get only 15 min to eat, but they at their desks. So they just get up, go to their back packs, get their lunch & sit back down again. Between that and snack time in the morning it seems fine (except for DD10 who nibbles like a mouse - arrgh). After their 15 min eating time, they go outside for 30 min to play.
Jaylivg that 5 min silent lunch thing is ludicrous. Does your son have an IEP? Could there be something added to it to cancel this out for him? (Forgive me if this has been mentioned already - I haven't read the whole thread yet).