My neice and nephew did the pirate cruise on Thanksgiving morning a few weeks ago and really enjoyed it. My sister and I (we weren't staying at the GF) enjoyed looking around at the resort, we did some shopping there as well. You can always boat on over to MK if you're going to the park that day anyway and do a little Main Street shopping or nibble on some candy or baked goods there. I do know that the kids were a little later than we anticipated, but they were so grinning from ear to ear about everything.
You can also take the boat over to the Poly from the GF too for some resort touring, shopping, of a cup of coffee at Kona's.
The kids will have a great time. My 5 year old nephew wore his pirate hat all Thanksgiving day and enjoyed all the CM's asking him about the treasure hunt!