also, while you're in the comments, have you thought of a transition system rather than a level select? I assume you want the events to be repeatable because you can pick the levels and since its one park if you just make closed door models on the ends of maps that open with the end level prompt and lead to the next level it wouldn't be a loading issue as your loading the same amount just changing where the load prompt is. It would help with game smoothness. I also get that each new idea you like is just going to slow production though, so do your own thing; all the ideas here that aren't bugs for the most part should be secondary to the creation of the base game.
It wouldn't be too hard to do, but not currently the experience we are going for. When we only have a few levels I think it's best just to enjoy the level itself, and then move onto the next. Don't really have any plans for like a world map to explore at this point, but will always consider things as the game gets bigger.