I recently took my almost 3 year old camping, it wasn't as awful as I expected!
Blow up beds not great for more than one person (if one person moves, the other one does too), proper self-inflating mats are supposed to be warmer & comfier. If possible, take a duvet/thick blanket as well as own pillows and sleeping bags. We also needed thick hoodies/cardigans and hats to sleep in, it gets much colder at night than you think it will.
You can get black out tents- I thought the one I bought was but it wasn't as dark as I expected, however, she didn't wake up stupidly early and I had my eye mask.
The first night, let them stay up as late as they want, I tried to put my daughter to bed at 9pm but she was just too excited! Eventually went to bed at 11 and slept until 7:45, then the next night she was ready to sleep by 7pm and slept all night until 7am.
Take a cool box with plenty of ice blocks and the night before you go, freeze a bottle of milk and put in the ice box before leaving, keeps everything cold and milk stays cold for a couple of days- good for cereal and coffee!
Plenty of toys and books, and plenty of snacks, cartons of juice etc. Big bottles of water too.
Finally, one of those cheap camping stoves and a gas canister. Great for making coffee, heating up beans, frying eggs etc.