Disabled guests would be realistic but it seems like it would be too much. I hope we get secoruty and staff on golf carts and segways.
The real question we should be asking is how can we make it fun to have disabled guests in the park... Which in my mind boils down to three things:
Character design.(I see no reason why the designs for disabled customers would be any less fun than those of our able bodied guests)
Personality/character interactions. What would having systems in place to cater to wheelchair/scooter bound guests bring to the table?
1.Elevators: Yes this might seem boring, but remember: The disabled guests wouldn't be the only ones interacting with the elevators, and I could easily see a bratty kid pushing all the buttons on it as one possible interaction.
2.Electric Scooter Rental: Again, not only would this make your park more appealing to the wheelchair bound, but also bring with it more opportunities for mischief to occur in your park(Can you imagine for instance your poor security guard trying to stop some kids from using the scooters for an impromptu drag race up and down the paths while other peeps dodge out of their way? Because I can...)
3.Stairs: Wheelchair+Stairs(Or any sufficiently steep incline) can lead to opportunities for some slapstick humor, or even some exasperated grumbling from the poor sap that has to push the wheelchair or baby buggy up the steep incline... Or situations like the union station scene from the Untouchables(But with less gangster shootouts and blood and more slapstick good times as peeps freak out over the runaway chair or baby carriage bouncing down the stairs or rolling down the hill. Bonus points if some wheelchair bound peeps or children want to do it again.)
Technical/game-play challenge. I think the challenge of developing park that has at least some things to amuse disabled guests would be a fun one that adds some more depth to the game...
Like:
"Is this ramp too steep? Will I have runaway wheelchairs/baby buggy's/wagons rolling down the hill and scaring the guests?"
"How will I blend the elevator into the theme?"
"Do I have enough security guards to keep bratty kids/teens from steeling the handicap scooters for a joyride?"
"Will my park still amuse guests who can't/won't go on the rides I have available?"(Because lets face it "Wheelchair accessible" also means "Baby carriage" friendly, which could get some more families going to your park too.)