Is it just the 2 of you or the all the little ones too? 17-19ft will get a little small with kids and bad weather, so make sure you pick a weekend with great weather.
As for the rental part, read the contract over good so you know what is and isn't expected. The dealer near me that rents, pretty much expects is to return in the same condition it left in. Clean and tidy with full propane tanks. Also check what comes with it. You'll need your bedding, will you need hoses and such?, comes with dishes/utensils? Check insurance, they will probably have some available (like a rental car) but you may be able to get it cheaper with better coverage from your own insurance provider. Also check it over to note every ding, broken hinge, stain, etc. and make sure everything works before you take it (fridge, water heater, furnace, water pump, etc). Pretty much just like renting a car.
As for campsites, that's personal preference. Some need 3 acres minimum to camp, some don't mind parking lots. Generally from my experience the average sites are around 30ft by 40ft. Most of the time a back in site will be more roomier than a pull thru site. Pull thru's are usually longer and narrower, but tend to be full hookup (water, electric, sewer). Smaller trailers have smaller holding tanks, so if it's gonna be more than a weekend, might want a full hook up site with sewer. Back in the day friends of ours had a good system when camping with there 3 small kids. Mom and dad took showers and used the camp bath houses, and the kids took baths in the camper. Made the holding tank last a little longer. Also the nice thing about a site with sewer is that there is no waiting around at the dump station. When you pull off your site you are on your way.
For the most part KOA's are nice campgrounds, with most having activities for the kids. But they are usually more pricey than other campgrounds. My thoughts are to find a spot you want to go, whether an amusement park, woods, tourist area, whatever. Then look for campgrounds in that area. You can do a google search, or there are apps that can do the same thing. All Stays Camp and RV, KOA, Good Sam Camping, etc. Franchise campgrounds (KOA, Jellystone, etc) are good, but sometimes a private park or even a state park can be a better experience. Another thing I've been doing is when I choose a campground I haven't been to before, I'll bring it up on google earth and get an actual birds eye view.
Anything more specific don't hesitate to ask. I envy you guys down south. I just winterized mine last weekend and already feeling cabin fever set in.
