Side story, as I mentioned above, I tip the escort to the site as well as anyone who delivers firewood, food, propane, etc. We frequent one particular campground many times a year and I keep up this tipping pattern there.
By the end of the summer, we end up with lots of "perks" from the campground staff......bundles of firewood just magically show up, kids get free ice cream when they go in the store, I even got a sweatshirt and the girls got t-shirts the last weekend we were there in the fall.
Do I tip expecting anything in return....no. But, you definitely can tell that the staff notices it and it is obviously appreciated.