I have never owned an RV and am contemplating going out full time with my wife and two teen aged kids. As much as I think a fifth wheel would possibly give us the most living space, I feel the cost of...
I would rent something and go on a few trips to see if the family really likes it before spending my money.
Personal experience says, that as the kids get older they will not want to be away from their friends, sports or other activities.
I also think you are better off with a used truck and 5th wheel. If you get a 2-3 year old old truck, you can likely by a factory warranty that will be good at any dealership.