Dinner at the Castle does NOT have Princesses coming around to the tables.
Part of the package is having your photograph taken with Cinderella on the first floor, then you go upstairs to the dining room.
During dinner the mice dance around and Fairy Godmother dances and sings, but no Princesses present.
The show with FG and the mice is a bit loud and it involves the lights flashing, and FG dancing between the tables randomly touching children (and sometimes adults) on the head with her wand. The mice seemed to make it to almost all the tables to kind flit about and then move on, occasionally lightly touching someones arm or chair.
You MAY be able to ask that FG and mice not approach your table (though logistically they may say they can't guarantee it of course), but I don't think there are any tables where you'd be shielded from the loud music/singing or the flashing lights. So it may not be a best choice for your son, unfortunately. It is VERY cool to be inside the castle eating while the fireworks are happening outside....you see the colored flashes of light outside the windows and hear the bangs.