How old are the kids? Just went camping with the whole family this weekend with a 5 year old and 2 year old, and all 4 of use slept in a Tepui Autana. Was a little cozy inside, but doable. I didn't think we would all fit, so I brought the annex along as backup and also had a spare mattress inside the car but we didn't use it.
Even the 2 year old can climb up the ladder without help, but I always watch them when coming down. It's a little more trouble to get them up there when they're sleeping, but still can be done by one person. I use a mini carabiner to lock the zippers at night when they go to bed so the younger one can't open it and fall out.