We are going on and Oasis-class ship for the first time this summer, and I can't wait! In 20 cruises I have never seen anything as anxiety-inducing as the pools on the
DCL Magic. We have found that the number of passengers and size of the ship are not as important as the layout and flow. My kids don't usually like the kid's clubs, so we are looking forward to trying lots of the different family activities together on the Oasis. I am also stressing about planning the dinners and shows, but we have scheduled early dining as a fall-back.
We usually look at the daily planner each evening and mark the things we MIGHT be interested in doing the next day. Each person chooses one thing they want to do most--maybe a show or the water slide or a specific meal/restaurant. Then throughout the day we DO NOT try to do everything happening onboard. As the day goes on, we decide what we want to do based on timing of our top picks but really just relax and play it by ear. If we don't get to something one day, it becomes a higher priority the next day.
DS also has anxiety and special needs and prefers to avoid loud crowds. It's great if you can decide major things you DON'T want to do and head to a different part of the ship at that time. The pools are empty during the major shows, and trivia/game shows are fun during the mega deck party. Specialty restaurants are much more relaxed at 5:30 than 7:30 and room service beats the buffet for breakfast any day. We have 2 adults and 2 kids, so DH often brings food back to the cabin for the ones who don't feel like facing the crowds. Even movies by the pool or doing a puzzle in the library can be great ways to relax. A favorite vacation memory is sitting on an open side deck reading and pointing out dolphins to DS playing on his ipad next to me. Bigger ships have more options, but you shouldn't feel like you have to do it all.