We just did this this past December. We were given advice to see the first show (I think its at 5:00) since it is an outdoor performance. If you do the second or third show, you can hear the show before you going on while you are in line. We did the first show once and then the latest show once since we already knew what we were going to see. Just an fyi.
And yes, just call the reservation line and they will tell you the available reservation times in order to make it to your chosen show on time.