Others will come along with more detailed info, but the four kids and all of their related paraphernalia inside of suburban putting weight on the rear axle will severely take away from what's left of the overall weight carrying capacity for the trailer hitch. And of course don't forget the dog's weight and his 20#s of dog food for the trip.
I think subs are great vehicles, only you really need the 3/4T version. I know you've got a lot of expenses with the four kids, but with all of the weight you're going to have to buy a small trailer which they're going to rapidly outgrow. If there's any way possible, I'd try to trade the 1/2T for a 3/4T so you're not so limited on trailer choices.
Have fun.
Bill
