I've got a 26' trailer...30' total tongue to bumper. Tows fine with my Sierra 1500. Weight is a key issue from a safety and a capacity perspective, but if you are within your weight capacity, the size of the front of the trailer (square ft) impacts towability as well. You're towing a big parachute behind you... Doesn't matter as much how long the parachute is behind you, but how big it opens up.
As far as kids/grand kids are concerned, I have limited experience. Having had my trailer less than a year, we've been out about 6 or 7 times. Only once with the grand kids so far. Not saying it won't happen more in the future, because we do want to bring the grandkids with us. But, in all likelihood, their parents will not go, because they would be looking forward to the break. And if they all come, they will have to bring their tent, and their separate vehicle, as my trailer only sleeps 4. I don't have the dinette that turns into a bed, opting for chairs only.
Yes, gas stations can be a challenge at times. Diesel guys have it great, as they can go into the truck lanes at truck stops.
Mike