We recently got back from an ABD to Costa Rica with our two kids, who are 5 and 11. Our 5 year old LOVED the trip. She would not have loved a trip that was all about museums, but she loved Costa Rica and had an amazing time. We actually chose ABD because we thought she would rather travel with other kids. (She was disappointed that she couldn't zip line or whitewater raft - she is my little daredevil. Those were the only two activities she was too young to participate in.) We have also done 3 Disney cruises and Aulani with both kids, plus and Alaska cruise not with
DCL. We also did a Europe cruise not with DCL when our son was 5, and it was amazing for him, but we really picked shore excursions around his interests more than half the time. I do not think the Mediterranean cruise would have worked quite as well for our daughter as it did for our son - so much depends on the individual child at that age. That said, we are seriously considering one of the ABD river cruises for next year, and she'll only be 6.
We loved Aulani. It was great for both kids, and the kids regularly ask to go back. We had a really nice mix of time together and adult time while the kids were at Aunty's Beach House, the Aulani Kids' Club. We split our time between Aulani and another hotel, and we did all our sight seeing while at the other hotel. Once we got to Aulani, we just hung out there. It worked really well for us.
We did Alaska with Princess instead of with Disney, because I was afraid the princess crazy 5 year old would remember princesses instead of Alaska if we went on DCL. Both kids absolutely loved Alaska on Princess. Alaska is spectacular, some of the most beautiful scenery you will ever see. We did a ferry to a shore excursion with a group from DCL, and they were having an amazing cruise, too. You can't go wrong!