We just came back from the 4/13 Wonder sailing. We chose the second seating and were happy overall. My son missed some of the fun activities in the Oceaneer's Club, but still enjoyed the movie time that they had later in the evenings.
Our one regret was that we missed the "adult" performance of the comedian (his earlier "G-rated" performance was hysterical). His only show was from 10:15 to 10:45 pm. By the time we left Triton's and dropped our son at the club it was 10:35. We thought we could catch the end, but the club was full. A group of us stood outside trying to hear what we could.
One benefit of the second seating was that we saw the early show. It was never too crowded so we always had great seats. The one night we ate at Palo's, we went to the later show. It was packed and was full of very young children and babies.
FYI: On the last morning before you get off the ship they serve two seatings of breakfast. If you have the early dinner seating, you must be at breakfast by 6:45 am. The later seating starts at 8 am. We appreciated having a little extra time to pack up in the morning.
Enjoy your cruise!