Ok, so the roads aren't great and there are 5 of us that need to go on a trip. I need 3 adults, an 8 year in a booster and a 4 year in a harness. what would allow the most room for the adult in the back? I have a Frontier, True Fit & Nautilus for the 4 year old and a Parkway, Monteray and a backless Turbo for the 8 year old. I would prefer a back I think.