Arrive at the port by 10:30 so you can be ready to board as soon as the ears open, that gives you a longer first day. We boarded, ate lunch, toured the ship a bit, went to rooms, and went swimming all before the sail away party. The first afternoon is the emptiest I saw the mickey pool.
Do the early seating. It does make the afternoon a little rushed at the end but it was nice to sit and relax a bit and gear back up for the evening activities. The kids can eat and then go the clubs to hang out while you finish dinner and the join back up for the shows. They were all great.