Dianna,
With so many great choices, it's always so hard to choose just one park, but if it was my choice, I would choose Magic Kingdom park and
Disney's Hollywood Studios. Disney's Hollywood Studios has always been my son's favorite park. He loves Toy Story Midway Mania!, Disney Junior - Live on Stage! and visiting some of his favorite Disney characters, such as Buzz and Woody and Phineas and Ferb. If your grandson loves cars and action, he may also enjoy Lights, Motor, Action! Extreme Stunt Show. Dining at Sci-Fi Dine-In Theater Restaurant while we are there is also on my son's "must do" list and finishing the night off with Fantasmic! is something we cannot miss.
As for a character breakfast, my personal favorite is '
Ohana, located inside Disney's Polynesian Village Resort. The food is outstanding and you are sure to get a lot of hugs from Lilo and Stitch.
Chef Mickey's is another family favorite. Located inside Disney's Contemporary Resort, it is a wonderful way to start off your day. My son and I also recently did the Disney Junior Play 'n Dine breakfast at
Hollywood & Vine, inside Disney's Hollywood Studios and he had a great time meeting his favorite Disney Junior friends.
Dianna, you know your grandson best, and no matter what you choose, I know he will have an unforgettable time.
If I can help you with anything else, please let me know.
Happy planning!
~Ana