I'd say, just because our daughter 3 (now 5) loved it the last trip...
Play-N-Dine breakfast
Princess breakfast in Epcot (Akershus)
Crystal Palace breakfast
Chef Mickey's Dinner
Biergarten dinner
Whispering Canyon Cafe lunch or dinner
She liked Sci-fi, but the food there isn't good at all and trust me, I'm not picky. We are skipping Whispering Canyon too because we want to try a few new places and something had to be sacrificed. Plus, I learned how to make ribs and pulled pork at home, so I can live with skipping it this time.
We are going to hit 1900 park fare this time for dinner so she can see Cinderella. We never did the two credit meal in the castle so I can't comment on it, but 1900 Park Fare, plus the Akershus princess breakfast in Epcot gives you two meals and a chance to meet almost every princess for the same amount of credits. You might want to consider that, unless they have their hearts set on eating in the castle. You could cancel the 2 credit ADR if you are able to get the other two booked 90 days out.That's up to you. You can't go wrong either way.
Basically the play-n-dine, akershus, and crystal palace are great experiences. We liked Chef Mickey's too. You may be able to book that one right now.
Whispering Canyon has fun and games the kids enjoy and my daughter loved the band and singing/dancing at biergarten.
The thing I'd do is try and book breakfasts with about 1/2 hour left on their schedule. They won't rush you or tear anyything down and keep serving fresh food, but you get two advantages...
1. Once they stop seating people, seats empty and are not filled. This means the characters have fewer stops and will visit your table more, and they will stay longer. At the play and dine, Jo Jo and Goliath came by so many times I was ready to feed them. Our daughter didn't eat much buut felt like she had them to herself. Definitely worth the credit!
2. If you book it on a day the park opens early, you can go in an hour before the park opens and get every major ride out of the way before you eat. For example, our play-n-dine was a 10 or 10:30 ADR. We rode tower of Terror and Rock-N-Roller Coaster 2x each, Star Tours once, watched a High School Musical show, then just sat around for awhile before we ate. Good luck doing all that in the afternoon!
If you book an earlier breakfast, you will be eating and missing out on this valuable time. Then you can leave the park if it gets too crowded and do something else like swim, nap, etc. You won't be missing anything during that time because the lines are too long. Then you can go back to a park in the early evening when everyone else is tired and ready to leave!
This is the only way to do it and enjoy yourself in my experience.