I agree with MichelleWV, he is 10 not 6. He needs to suck it up and stay.
I just don't understand if he wouldn't stay at grandma's and a good friends overnight, what made you feel he would stay at an overnight camp with a bunch of strangers.
My DS just turned 11. He just returned yesterday from a 4 night overnight camp. He was a little homesick, I could tell, he called me twice a day. But he would never say he wanted to come home.
IMOP, your son isn't even giving it a chance. He knows mommy will come get him on a whim , so why even try to have fun. No way would I be driving 5 hours in the dark pouring rain. I would be mad about the location change, but I would deal with that when I picked him up at the end of camp.
Why didn't you send the allergy meds with him?