Isn't that the point though? It's after hours, well after park closing, you don't have to go, even if you're on park that day, and likewise you don't have to be on park to attend. It's just a case of the park diversifying and using their land to try other things.
Nobody bats an eye lid when a farm puts on a Halloween event.
Nobody cares when stately homes or race tracks host music festivals.
How about pubs having Christmas fairs?
Reactions to this stink of thoosie entitlement, like "I'm just salty there'll be people on park, but I don't get to ride the coasters for longer."