OP, based on your kids' ages, and the fact you want this new trailer to last at least 15 years, I would just go for the travel trailer with lots of living space. It's easy for little kids to sleep in smaller spaces, but in 15 years you'll basically be 5 adult-sized people in that trailer. Since you've got the budget and aren't going to be moving it often, go for something that has lots of space, both living and bed-wise (ie a bunkhouse style trailer.
Also, I can't think of any toy hauler that can be remotely pulled by a 1/2 ton truck and still have comfortable living space, that would also be able to fit 5 full size quads anyway, so having a separate trailer will probably always be a thing. You can also upgrade your truck later if you did decide to not have it parked at a seasonal site.