This is what I do......Quick walk and easy exit. Yes will be more expensive but the more people in the car, the less premium.
If concerned about leaving early, this give you the max time at camp as there is no wait. I went to camp on day 2. I drove to Henrietta and 3 errands. Then drove by the school where busses where being unloaded an hour after camp closed. The lot still had many cars so the wait may be long. Parking across the street is most time effective.