Suggest Treatment For Fatigue,headache And Nausea

I believe my 6 year old has expereince heat exhaustion 3 times in the past two weeks. He comes home from day camp fine - and then as we progress into evening is tired, headache and nauseous. I 've provided a cool show and sipping gatorade. And talk to him and the staff counselors about drinking more fluids. Just wondering if I should be considering another ailment.