Does it cost money to park 3 charter buses full of school children at the zoo? Where would the buses park?

Their website has field trip section. They should have some promotional offer/discount for school children field trips and buses parking.

You have to pay to park, but call the office at happy hollow to find out what prices would be for your group.

There is parking for buses in the pay lot. Generally you have to pay, but they can call the office and see if there is a negotiated group rate discount.