I think we're going around in circles here when really the answer is right in front of us. You clearly care very much about how to explain your park is fictitious -- and that's fantastic!
But most others aren't worried about this. So, do whatever makes YOU feel most comfortable, and I promise, no matter how strange that may sound, folks reading it will play along. Everyone just wants to see your original ideas -- and don't have to worry about whether it is fictitious or not.
You don't have to world build an entirely original city or universe just to set an original theme park. If you want to, you can. If you don't want to, you don't have to. Do whatever you feel is most comfortable and "right" for you, and everyone reading will follow.
But there are a couple of holdups, as I said. The first is how to end the Soarin' ride, which will be in the park. It usually ends in a park it's found at (Disneyland (as opposed to CA Adventure), Epcot, Tokyo DisneySea) or the city the park is found in, as in Shanghai Disneyland, which ends in Shanghai proper, rather than at Shanghai Disneyland.
The thing is, I would like to have something unique in this park, called the International Expo Gardens (working name), which is the hub of the park. This is where Small World will be found as well, rather than in Fantasyland.
I'm also thinking of having Portuguese and German as the spoken languages in the park. How do I determine which ones to use for the attractions? Because I can't possibly use both on the entrance signs or in the rides. And no, shows don't count.