My 12 yo son wasn't thrilled, but since he has three sisters, he often has no choice but to be dragged along on the girlie outings. Honestly, he was fine just with getting to eat the food. We had a table for six and he sat on the inside so the girls were all on the outside of the table (where the characters could get to them easily).
At one point one of the princesses starting teasing him a bit about being out with the girls and not having his picture taken with the princesses. I have a priceless photo of THE FACE ;-). When Wendy arrived at the table she told ds he had to have his picture taken or she'd come and get him -- even under the table if it took that -- all said with a proper British accent. What a memory! As much as he blushes when we talk about it, there is still a smile in there!
I know my ds is 12 and yours is much younger, so the dynamics will be different, but I think it is a great experience. This year we will be at WDW on ds's birthday, but I'm not making him see the princesses that day -- just Minnie, who will be even better for the pics!
Only two more days until we leave... we can't take the waiting anymore!!! Can't wait to get back to that Disney Magic!