They do not close the gate. There is self registration after hours.
Your getting into the last few weeks of the season, there is no gate to close but there won't be any sites later in the day on weekends. There are many ''last minute'' campers who try to take in fall's amazing sights.
It's first come, first serve, and it fills up quick. Best to get there before 4-5 to ensure a place to camp.
In the fall you should get there early anyway because finding a site in the dark is not easy and can be dangerous. If you are asking can you get out after dark and back in if you drive up to the lodge for dinner... The answer is yes, but it is an easy walk on the trail instead anyway.
Thanks! Your answer is awaiting moderation.