Hi Nevaeh,
Let me start by saying that breakfast at Chef Mickey's is a fantastic way to start a day at Walt Disney World!
If you are staying at a Disney Resort hotel, I would recommend returning to your hotel for a couple of hours early afternoon if you will be getting up early and have lots planned for that evening. That way, they can have a couple of hours sleep or just have some down time to relax in the pool.
I must say that my now 9-year old Son has always coped very well with long days during our previous trips.
There are lots of places where you will be able to find Mickey Mouse. Here are just a few of them:-
1/
Town Square Theater at the Magic Kingdom Theme Park
2/
Epcot Character Spot at Epcot Theme Park
3/ Camp Minnie-Mickey at Disney's Animal Kingdom
Wishing you a magical trip filled with memories which will last a lifetime!