I hadn't gone camping in summer for something like 20 years. It's always rainy, and exceptionally wet and hot here in Hong Kong. This is a breakthrough to me to serve 20 kids in a local campsite. When we said a campsite, we have bath room and we can have meal without cooking and indeed, we just cooked our own breakfast.
To tackle the hot weather, I have another camp which has good ventilation, and I have a small fan inside, powered by 3 18650 batteries in series. I found that a set of 3400mmAh battery could last for a whole night.
This time I have so many 18650 with me, 3 for another small fan, 6 for a portable mobile charger, and another 6 as spare, and also 1 with my tent lamp.