If your wife is able to drive I think it would be far cheaper to have her follow you with a few kids in another vehicle. Even if expense is of no concern to you, I don't know of any place that rents an suv that allows towing and would have a brake controller.
Another thought...since I'm guessing a 5 week rental that would allow towing and for that many miles would cost easily in the thousands, an option would be to buy a reliable suv for the trip, put a few thousand miles on it, and sell it for what you paid for it when you return.