Are you staying on-property or off? If you're staying on-property, you'll get priority seating at most Citywalk restaurants (excluding Emeril's and Bubba Gump) by showing your roomkey.
Both Emeril's at Citywalk and Emeril's Tchoup Chop at RPR usually require a reservation for dinner. So if either one is in your itinerary, I would make a reservation for it.
In the past, I haven't made reservations (except for the two Emeril's restaurants and HRH's Palm Restaurant) , but Opentable.com is so easy to use that I may use it for reservations on our upcoming October trip.