I cannot caution strongly enough that it's important to test out your child's reaction to "live" characters before investing in a character meal. Many children react to live characters with extreme fear, and if that is the case a character meal will NOT be a good experience. (Trust me, I learned this the hard way.)
Be sure to take your child to some kind of local event with costumed/furry characters and try him out on the interactions before going to WDW, or if that isn't possible, book a refundable character meal toward the end of your trip the first time, so that you have a few days to gauge reaction to characters in the parks first. An expensive character meal with a screaming child who dives under the table and refuses to come out to eat is no one's idea of fun.