I have to agree, there isn't much to gain with a MH. Legally (and safety wise), the kids have to be seated and belted in.
I also wouldn't count on it being any easier to drive assuming you are towing a car with the MH. If the wife is intimidated by the 5th wheel, she will likely be intimidated by the MH.
How many weeks are you looking at for a cross country trip? 500mile days on a 4000mile each way trip is around 16 full 10hr travel days. Even if you force the miles and do 1000mile days, that's still 8 travel days. Anything short of a month (preferably at least 6 weeks) sounds like punishment for the kids. Handing them a coloring book or a Gameboy isn't going to change that.
