Hi Mark!
How exciting that you're taking your son to Walt Disney World to celebrate his 4th Birthday! He will be at such a perfect age to really soak up all of the magic!
Chef Mickey's is an excellent choice for a Character Dining experience that he'll truly enjoy. This Character buffet at Disney's Contemporary Resort is open only for breakfast and dinner daily.
If you'd prefer to visit closer to lunch time, the latest reservation time available is at about 11:15am. The menu includes a large variety of breakfast and brunch items, from waffles and pancakes to potato dishes and eggs, as well as cereal, pastries and more. Pricing for breakfast/brunch is currently approximately $31/adult and $17/child, not inclusive of gratuities. Following the Character Buffet Breakfast, Chef Mickey's closes to prepare for the Dinner Buffet which begins seating at 5:00pm.
If you'd really enjoy a Character Lunch experience for your son's age, consider the
Disney Junior Play 'n Dine experience over at Hollywood Studios' Hollywood & Vine Restaurant. During this lively, musical meal, you'll visit with June from Disney's Little Einsteins, Jake the Neverland Pirate, Handy Manny and even Special Agent Oso! It's lots of fun for the little ones. Reservations are available for both breakfast and lunch at this location. Lunch reservations are taken between 11:40am - 2:25pm and pricing ranges from $31-36/adult and $17-$19/child, depending on the season in which you are visiting.
I hope this information is helpful to you Mark.
Thanks for visiting the Moms Panel with your question. Please write me back if I may be of further assistance to you as you plan your son's birthday trip!
Wishing you a simply Magical time celebrating at Walt Disney World!
Kirsten