If the only use of the TT would be for the annual family trek, then it is not the way to go. Additional fuel cost, driving time as well as the cost of the TT and a proper tow vehicle would make the cost higher than travelling in a typical minivan and renting a cabin, house, apt or whatever.
In many areas there are extended stay suite motels which can be rented for $350 to $700 a week. That would provide a comfortable stay for the annual trip, and it doesnt require maintenance, Monthly payments, Additional driving time, or additional fuel cost.
If you want to take up camping because of moving to a great area for it, and think it interest you for that as well, that totally changes the dynamic.
I'd suggest then that you wait until you are out in Boise, and rent a camper a couple of times to see if that is an avenue you wish to pursue.