The big thing to watch for with a larger C and a large family and gear is the carrying capacity of the unit. If it has a Ford V10 engine, there are some with multiple slides that can only carry 1500 pounds or so. Also, you have to consider the use of seatbelts, and whether you are happy having four kids with only lap belts and no headrests strapped into a relatively small dinette.
I think you should stay with a towing vehicle, and look at trailers with accommodation for the kids and pet. There is bound to be times when someone has to be somewhere, and you will want to have the ability to take a vehicle while everyone else stays behind.