You've gotten a lot of options. We hadn't planned on going into a park at all on check in day. We had an ADR at Chef Mickey's, and the girls could not WAIT to get in to see the castle, so we went. We didn't go any farther than Main St, and we let them get their ears in the Chapeau. They got to look at the castle, had fun trying on their ears, etc. Just be prepared that if they can see it, you might have a fight on your hands to go to it!
For check out day, I would try for the latest breakfast ADR you can get. We ended at Chef Mickey's, too. I think our ADR was around 11am? It gave us time to pack up, get over there, and say goodbye to Mickey! We waved goodbye to the castle (and cried).
So for dinner, Ohana is great at the Poly, then you can see Wishes from there. But we wanted our kids to see the Mouse ASAP. You can take the monorail to the Poly if you want to watch Wishes from the beach after dinner.
Check out morning, breakfast w/ Mickey, Goofy, Lilo, and Stitch at Ohana might be a good option for you if you've done Chef Mickey's for dinner on check in day, so they can say goodbye to Mickey!