Excellent advice given above. While we have towed our travel trailer to FL several times (from Chicago) one year we rented a 31' class Cfrom Camping World and drove to Orlando and back during winter break. A stop to Walmart bought us all we needed for the trip. We tend to pack heavy and since we have TT experience we knew what to buy. Just in case you forget something there are numerous Walmarts and Camping Worlds along the way. That year we stayed at several of FL state parks and experienced a new style of camping compared to Yogi Bear. One stop we were at a manataa refuge another we literally were on the beach (Flagler city). One year we flew to FL and rented a 31' Class C (El Monte) so like you we had our suitcases to start with but again a quick stop at Walmart got us what we needed and we stayed at Disney RV Campground.
With the El Monte rental the MH wouldn't start at the end of the night at Disney World but a call to their roadside assistance directed me to a loose nut somewhere in the electrical system. In the Camping World MH the slide got stuck out at a truck stop but it was extremely cold and their roadside helped me then also (breaker?). Try to get a grasp of the systems during the orientation or and read their rental handbook if the have one.
Realize that the fuel economy probably won't be as good as the rental salesperson says especially if you are going over 60 mph. I think they told me 9-10 mpg but speeding there in the cold going through the mountains it was more like 6-7 mpg.
Your family will enjoy this, while I'm writing this makes me want to do it again lol
