With most of the more popular restaraunts booked up I don't know. Why not go ahead and make an ADR just in case? Last Dec we had an ADR at 7:30pm, but were tired so showed up and asked to be seated about 5:30pm and got right in. There was only two other couples in the whole restaraunt.
FYI: I've posted this before but I'm still amazed at the amount of food on the Mixed Grill. If you order it be sure to have someone to share with. It's good, but HUGE! My mom and I both ordered it, ate until we were full, carried it back to our room, ate on it two nights later, and finally threw the rest away.