Hi Janice,
We had a similar situation on our most recent trip: more reservations than dining credits. To help us decide which to use on the dining plan to make the most of our investment, I printed out the menus for all the restaurants (nearly all of them are online here), put a large post-it note on each of them, & then had each family member place their possible order based on the specific dining plan's details. Once finished, I had an idea of which restaurants we would spend the most money in, which we then used our dining credits for. The others we paid for out of pocket.
I'd encourage you to keep your reservations to allow for some flexibility when you arrive at your trip since plans change, and it's best to keep more options available. I included the number for Disney Dining on my phone and then cancelled reservations we decided against as the day became closer to open up spot for other guests.
As for Shutters/Crystal Palace, it may be a matter of crowd preferences. At
Crystal Palace, you'll be in the heart of the Magic Kingdom at a buffet (will likely have some traditional holiday offerings) and with Pooh & friends. It will likely be crowded. At
Shutters, there won't likely be the same levels of crowds with it being at a resort & it is a table service with no characters. I'm not sure how much traditional Thanksgiving offerings will be there, however, but it may be fun to have Caribbean food on Thanksgiving. I'd weigh which options best fit your family's needs.