Most parks have a rule that pets should not be left unattended, but we haven't encountered any enforcement. As Long as they don't bark incessantly when you are gone, there will not be a problem.
Although our dog is crate trained for travel, in the RV we leave her free, run the fan and TV and she sleeps. She knows the clues we are leaving and jumps a on the bed to wait. We usually wait a day or two before leaving her alone, then she is comfortable with new scents and sounds of the park , and accepts being left, just as she does at home.