^^^I agree with the above advice about the tanks. If you use campground toilets, that will save you a lot of black tank space. When you start running out of gray tank space, you can fill up a few buckets from the gray tank and dump them through the toilet.
So far as weights---you want to look at the listed GROSS (max loaded) weight of your trailer. Assume your tongue weight will be 10-15%, I use 13% as an estimator. Others are correct, that will be part of the cargo of your tow vehicle.
You will definitely need a weight distribution hitch. I've been looking at them too, and it looks like the Andersen brand is the lightest weight to do a good job.
As a rule of thumb for towing, you want the gross trailer weight to be about 80% of your tow rating. Start with this number as a max for your trailer weight, and then do the math on cargo capacity as stated above.
I've done a lot of towing and in my experience about 60 mph is a good max safe towing speed. Get in the right lane and don't be concerned about who passes you. That's what the right lane is for.
There are lots of people on here who will tell you that you can't tow anything with less than a 3/4 ton truck. That's their opinion, and opinions don't matter. Just do your math as described above, and you will be fine.
Another option that might work when your kids get bigger, or want to take friends, is to let them sack out in the back of the tow vehicle. Lots of kids like to have their "own" spot away from Mom and think it's fun.
