Live shows - I've seen many theme parks hosting live shows and performances, so I would like to see that in the game. They'll probably have to be pre-set, since animating the shows will be a pain in a neck.
Parades - Some theme parks have these. You could plan a parade to occur during a regularly timed event, choose the floats, and plan the path.
Carnival booths - I've seen SeaWorld and Universal Studios having these. So, a guest could go to a random carnival booth and win a prize depending on randomized events.
Arcade - HECK YEAH! WE SHOULD HAVE THESE! But they'll have to be original, in order to avoid copyright.
TV screens - It should function like the Work at the Pizza Place TVs.
Petting zoo places - With live animals and such, especially to give a county fair or SeaWorld vibe. To ease gameplay, you don't have to pay regularly for food and care.
Stalls with T-shirts, plushies, houseware, you get the idea - More open than just hats. Oh, and you could use Roblox catalog items.
4D rides - Universal Studios has a heck lot of them and THEY'RE AWESOME! I think they'll just be rides with jittering and TV screens, though.
'"Dumbo"-like 'ride - You know those aerial carousel rides where you can lift your car up and down? That's right!