Last year my son (married, one baby and a Lab, they live off the grid in CA.) was looking to buy a Tacoma and I tried steering him towards a Tundra, but the tipping point for him was the gas savings. Now he wishes he'd got the Tundra for #1. the cargo capacity (size and weight both), #2. the interior room, #3. the towing capacity.
Regarding fuel mileage, based on 15,000 miles per year and figures from fuelly.com, it'll cost you roughly $600-$800+ more for the Tundra 5.7L V8 vs the V6 Ridgeline. (about 15.5 vs 18 mpg).
I'd go for the Tundra based on the points and concerns in YOUR post. Good luck and enjoy!