I was just getting ready to do on-line check in and our ME pick up times (both arriving and departing are wrong - both say am instead of pm). Is this something that I need to clear up now or can it wait until we arrive on Sunday?
I wouldn't worry about your arrival. Your scheduled to depart on any particular bus and your luggage (with yellow tags/resort name) will be pulled regardless.
You might want to correct your return information with the front desk as that is typically on a schedule.
To cut down the chances of something else screwing up, it is better to wait until you get there before fixing errors on the Magical Express part going home. Here you are assinged to a specific bus time.