Love the concept, I could honestly see this being a mod to Wii Sports Restort. You'd be able to walk around the island and when you get to a specific location a prompt will pop up to where you can select the sport associated with that location. Say you walk up to the basketball court and you can select to play a game. Kinda like Nintendo Land on Wii U, where you can swap between either using the menu to instantly choose the game or walking around the plaza and moving yourself there. If you plan to go further with development, definitely consider adding random miis scattered around doing their own thing. It could be as simple as just them doing a basic walk cycle in a set area, but it'll at least help players not feel alone.