That would depend on what you need it for. There are an awful lot of "higher ups" at Disney World. You looking for someone in Foods, Resorts, Entertainment, Admin, College Program, HR, Finance, Legal, Marketing .... ? If it's a general complaint or complement, those will all be re-routed anyway, through the general guest services e-mail. If it's an idea or suggestion for anything new, it will be automatically routed to Legal.
If you're honestly trying to reach Al Weiss, e-mail won't get to him. It'll go to his assistant, who will route it to who it needs to go to to deal with the question, concern, problem, idea ... whatever.
If you could be a little more clear on what you wanted, I could send you to a more concrete location, but if you don't want to do that, then your best bet is to send a hard-copy of your comments to Al in a snail mail letter. It will still be opened and routed by an assistant, but having the actual letter as opposed to an e-mail, gives it a bit more weight. (Literally and figuratively!)
Al Weiss
Walt Disney World
PO Box 10000
Lake Buena Vista, FL 32830