First of all I would have to say which character dining you decide to do strongly depends on your own child. There are several different choices at WDW and some would appear more suited to a certain gender. For example, dining at Cinderellas Royal Table with the Princesses may on face value appear to be just for little girls, but I’ve seen many little boys come out of there with lip stick on their cheeks from the admiring princesses and big smiles on their faces.
Assuming though your little boy is not so into princesses or Mary Poppins (ruling out CRT, Akershus Royal Table and 1900 Park Fare), it again depends on which characters he is most into.
I’m going to recommend two which I have just recently done myself, albeit it with a 2 year old girl.
Firstly, if he is still into Disney Junior, Play and Dine at Hollywood and Vine in Disney Hollywood Studios is just great! When we went there last week we met Jake (from The Neverland Pirates), Oso, Handy Manny and June from The Little Einsteins. There is lots of interaction and as you would expect from a Disney Junior venue lots of singing and dancing. The buffet was good too, plenty of choice ie cereals, bakery, fresh fruit, cooked stuff like eggs and bacon and Mickey waffles. This was $26.99 plus tax per adult and our 2 year old was free.
The second recommendation is Cape May at the Beach Club. This was amazing! The characters here are Donald, Goofy and Minnie all in their swimming gear. There was lots of boys here and they loved all of the characters. Again, good interaction, amazing food (buffet again but I thought slightly nicer) and gorgeous setting. If your son likes these guys it is a great place to go. This was also $26.99 but I would have happily paid more.
Of course that is not to rule out any of the others where the famous Mouse appears. If Mickey is your sons Main Mouse then try Chef Mickeys, Tusker House, ‘Ohana or The Garden Grill. These are understandably very popular and it is usually necessary to make an ADR (advanced dining reservation) 180 days before your required date.
Have a wonderful trip!