We put our nine and eleven year old daughters and four dogs (fifty to seventy-five pounds) in the back seat of our 2500 Ram. It is a little crowded but they work it out pretty quickly. Two dogs sleep on the floor, one sits up and looks out the windows the whole trip, and the other curls up and sleeps next to a kid. One good thing is that it limits the amount of stuff that the kids pack into the truck, they generally just take a book or tablet and a blanket, not all of their worldly possessions and that makes loading up a LOT easier.
As for a trailer, we went with a Primetime LaCrosse 329 and have been very happy with it. There is room for family movie night in the living area on rainy evenings, a big bunkhouse for the kids and dogs, lots of storage space, and both indoor and outside kitchens. I originally thought the outside kitchen was not necessary, but quickly came to love it and we use it much more than the inside one. It has been back into the dealer once for a couple of little things right after we bought it (dripping faucet, sofa problem, a cabinet door that was crooked) but has been pretty trouble free since then.