We've been rebuilding derelict sailboats for 20+ years and have tried a few products. Our favorite, by far, for results and ease of use is Interlux Brightsides. It is a one-part polyurethane that goes on beautifully using the roll and tip method. We prefer it to a 2-part finish that has to be sprayed because it makes touch ups easier in our opinion. It is super high gloss, but they make a flattening agent to kill the gloss if you prefer that kind of finish.
We used it on our hulls and decks. The hulls came up alongside docks, had fenders banging on them, the decks got got walked and jumped on, had metal things dropped on them and kids spilling God knows what. A good scrubbing and they were beautiful again. A very hard, durable coating that comes in lots of nice colors. (No, I don't work for them.)
Since it's what we know, we will be building our teardrop much the same as we would build our boats. We figure if it will work in the marine environment, it should work in the campground, right?