If I recall, not many do, but my kids do. If he's into it, it will be fun regardless!
Last time we had a meal with Winnie the Pooh, it was at Tony's for lunch (while CP was being refurbished). DD 4 wore a Sleeping Beauty costume, DD 2 wore a Minnie costume, and DS 10 months, wore Tigger ears. He has red hair so he looked kind of orange, and furry like Tigger anyway!
The trip before, we had dinner at CP, and my oldest DD was 2 at the time, and she wore the Minnie Mouse costume and I dressed my younger DD who was 8 months at the time in a pink polka dot dress and pink Minnie ears.
My kids love to dress up and I dress them up any chance I get!
Have fun!!