Walk around the park, picking up trash and throwing it away.
This is not as much of a cheat as it is a hint. go to the waterworld show and watch it then exit. every time you do this you get 100 points. Keep doing this until you have as many points as needed.
Get Attraction Mode
First get all 8 stamps and then talk to Woody Woodpecker near the globe. When talking to him pick the magic show. Now when the credits finish go back to the title screen and see a option for attraction mode
Complete give attractions and the sun will go down.