Can you bring your dive computer and your own fins?
Why would you need a dive computer for an aquarium dive?
No issue with NDL limits at depths that will be at or less than 30' especially given that the dive is limited to about 45 minutes.
To my knowledge Disney is not supplying Nitrox on these aquarium dives (nor would there be any benefit unless you're one of those divers who believes that Nitrox results in less fatigue) and even if they did supply it, it's not likely that you'll hit your 02 limits during a 45 minute dive at depths at or less than 30'
Even if it's air integrated it's not like you're going to come anywhere close to emptying a tank during a 45 minute dive at those shallow depths and even if you did, an emergency ascent from depths shallower than 30' is typically within the abilities of the average diver. Also they supply you with a complete regulator set so you've got the SPG not that you're going to need to check it every few minutes if ever.
I guess if you have a tendency to ascend too rapidly you might want to have the benefit of the ascent alarm but that's just using gear to solve a skills issue.
Maybe the Epcot trip is in the midst of a week long dive trip and you're doing a lot of deep diving and that minute bit of additional Nitrogen exposure that is monitored and compensated for by the dive computer could make a difference between getting bent or not but that's a stretch.
Or your dive computer has a digital compass and you're concerned about not having the ability to navigate? I dived in the Epcot tank once and I don't recall that it was large enough to get lost in but hey you never know.
Or your dive computer doubles as your regular watch that you wear all day long and you're worried if you leave it behind someone will steal it and even if they don't you won't enjoy the dive because you'll still be worried that it won't be there when you get back to the locker room.
Perhaps you want to upload your aquarium dive into your digital logbook so you've got the detailed dive profile that will look pretty much like a flat bottomed bowl as you explore the bottom of the big fish tank, and at the same time you'll save yourself some data entry. That's about the only benefit I can possibly think of.
