We are not experienced cruisers, but did the land and sea package last Dec (stayed at the Poly) and really enjoyed it. We spent 4 days at the park, and felt we had ample time to run around and enjoy the MK and the other parks. On our last "land" day, we went to the AK. I do wish we had gotten there a bit earlier (we took our time having breakfast and leaving the Poly). We were kind of rushed.
The "sea" part went quickly. However, we didn't schedule any special activities like Palo or the spa. . . . just relaxed around the pool and enjoyed the food and service. DS 5 had a great time in the club.
We did a glass bottom boat excursion in Nassua, which I don't recommend. I am sure there are lots of great things to do there. However, on our next land and sea trip (Feb '04) we will stay on the boat, which is significantly less crowded at that time.
Good luck in your plans.