I did it once and was totally disgusted, it was so dirty in the area and we did not have any of the utensil we were supposed to for decorating the cake that they give you.
The upside was the kids loved it, it is in the outside area of the Plaza Inn, it was $10.00 when we did it, per person, but our 3 year olds were free. There was cake shaped like Mickey for each person with frosting and decorations to deck it out. Punch and stickers, and some bigger B-day buckets you can purchase with a bunch of goodies. Mickey and Minnie were there and there was a nice line to get your pic with them under a Birthday Banner.
I really should have complained at the time, because it was really bad! Having a 3 y/o with you however, limits anything you can get accomplished. I just felt bad because I really urged a friend to do it as it was her DD's B-Day that day. I did get a $1 pass holder discount.
I would hate to not recommend it, as the kids thought it was great.