As a PP said, lunch is tough right now for character meals. The best ones are breakfast or dinner only at resorts.
Will Crystal Palace be back to characters by the time you go?
And, if they open the lunch/brunch option back, Chef Mickey is another easy one from MK that my then 5 yo girls loved. You could book the latest breakfast they have and do breakfast foods for lunch.
Garden Grill is great. It was a particular request of mine to do again for our upcoming visit.
If you decide to do a dinner, Storybook Dining is awesome. The queen is excellent in character, the dwarfs are fun and don't meet regularly outside of that meal. But, it's not a lunch that gets you out of the heat of the day...