I found this site, pretty neat after you plug in all of your vehicle numbers.
https://goo.gl/zR9Yzy
It suggests sort of what you suggest ksu_i, the max trailer weight I should probably be looking at is around 5,333 lbs, if I purchase a weight distribution hitch.
As for weight of my family, I have 3 daughters that are all under 90lbs and projected to be no more than 5' 4". My wife is about 120lbs, I'm roughly 185lbs. My son is 10 and about 90lbs, probably end up being 160-170lbs in high school. We travel pretty light and I'd travel without water, however I still think the 30' 5800lb trailer is pushing it even if I travel light.
I found some older Ford Excursions but they want mint for those too....fun stuff. I could get a truck again, but traveling in a truck with 6 people almost takes the fun out of camping :).
