How much foes it cost to reserve a pavilion? And what time do we have to be gone?

They don't charge for the pavilion but they might be able to be reserved. I think the park closes around 8 or 9

It's 30 dollars to reserve a pavilion. We went on Sunday. You can reserve it online. I believe they tell you what time you can use it till. We saw some people still using one around 8 pm.