there are ALOT of variables....
size of MH ( 30 or 50 amp)/ diesel vs gas/ poshness of campgrounds/ meals planned/fuel prices
Prices to rent tend to be VERY expensive... so take that in to factor. Start pricing now....
As for fuel, try to stick with truck stops, they tend to have the cheapest fuel. You can track prices and location of most truck stops. Many, if not most, has freq fuel cards that give dicounts on every gal. Love's, flying J, etc.
Definately cheaper to eat in than to dine out... expecially with teens.
Try to map out a tenative route and google/yahoo search for campgrounds along the way....( the closer u get to AK the pricer they will tend to get) With teens, I'd recommend at least some with pools/activity rooms... to give them a break. Most truck stops will allow u to park free overnight as well as most walmarts and malls.... no ammenities but a good time to pick up supplies and it's FREE... another good reason to try to alter it with places that have things for the teens to do or a place for them to get out of ur hair and chill for a while...