It depends upon your goals. Do you want a D&D campaign set in a setting that is inspired by all of the various 'Lands' in Disney World/Disney Land? Do you want D&D characters running around in the actual Disney World/Land because they plane shifted into a world like ours? Do you want D&D characters to live in a cheerful Blade Runner style setting with animatronic servants, amusement services every 100 feet, easy access to unhealthy food, and packed streets?
If I were to run a game for Disney fans and wanted to capitalize upon their fandom (and for some reason thought it would be a good idea), I'd run a 5E game and start running Lost Mine of Phandelver. As the PCs explored the first adventure site they'd discover a portal. That would take them to an abandoned Disney Land / World. I'd use a real map of the park. I'd populate it like a dungeon for low level adventurers, but the edges of it would be shrouded in smoke that the PCs could not leave. It would end up being a Ravenloft Domain created by a tragedy that took place in the location. The Domain Lord would be someone that made a horrible, but mandane, mistake - perhaps something that ended the greatest Love of their life. However, each of the rides, attractions, etc... would have portals that took PCs to lands inspired by each of the rides. The trick for players would be that anytime they enter one of these portals they'd have a set time before the portal collapses and the land behind the portal disappears - with the Pcs left behind going with it. The PCs would need to explore these lands to find a way out of the Ravenloft Domain - using hints found in each of these worlds to piece together the mystery of the Domain. The escape from the Domain would only be possible if the PCs can 'relive' the events of that trauma to summon the Lord, and then end the Trauma (RP, combat, and other options could exist for the final climax). I'd try to run it so that the PCs would pick their next location at the end of a session so that I could prepare it.
