[GrahamBaby4]

We did this when we only had two, now we have a camper. But, First off, make sure you take glow sticks for the 2 yr old (walmart even has battery operated ones) it will make him/her more comfortable in the dark. And, Have the light sleeper (mom or dad) sleep next to the opening of the tent, even if it is a different direction than the rest of the family because you will know if the 2 yr old gets up to go somewhere. Always have their security item with them, blanket, dolly, whatever it may be.
Hope that helps a bit, don't forget the boob/bottle LOL sippy cups for the 2 yr old if he/she needs them and other "home" like items that you know make them comfy.