Help find Tow Vehicle large family 9 with seating for 12 min

The easiest option, if you have another driver, it to take a second vehicle. It's going to be difficult to find a vehicle that can carry that many people and weight at the same time. The problem is that most vans that can seat 12 people will have a max towing capacity around 10,000 lbs. So you have to choose between carrying 9 and towing much less or towing the full trailer weight with no one in the van except the driver.

Really the easiest all inclusive option would be to go with a bus conversion. You'll get a diesel engine and a real truck chassis. You have a lot of options to choose from like school, transit, limo, and shuttle buses. You can get some pretty ridiculous GVWRs for very little money. You can convert the inside to include some living quarters and you'd essentially have a motorhome pulling a TT.

If you went this route, be careful of the short school buses. Lots are typically built off of the 1 ton van chassis. The box that's built on the back has a good amount of weight so you'll end up with the exact same limitations as the off the shelf 1 ton van. Make sure it's built off of a commercial chassis like the one linked above. Also find a bus that's been geared for highway travel. A lot of your city buses are geared for street use and struggle go beyond 55.