[rjmunro]

All the money could go to the park from the lottery if they set up the contract that way. Alternatively, they could set up a contract such that the park gets a fixed amount per visitor no matter what the auction price ends up being.

I think they should do half the tickets by lottery, half by auction. Lottery tickets should require ID and/or photo upload when you enter to prevent reselling. The lottery/auction operator should get a percentage of the total money, with the park service keeping most of it.