Where to park the trailer after check out or early arrival?

As you can see the answers are extremely varied. The best thing is to contact the park in question and ask how they would treat it. Their answer might be entirely different in the middle of the high season than it is in the low season, so let them know the dates you are considering.

Many campgrounds will not let you reserve a Saturday only during the high season and will require a Fri-Saturday. They may also not care as much on Sunday as the places clear out as people go home to get ready for work on Monday.