We loved this in May with our girls ages 5 and 7 at the time. Make sure if there is a Photopass photographer right when you check in, that you get a family picture with the castle lit up in the background. We had PP+, and my girls wanted to have their picture done with every different color of the castle lighting in the background! Since most other families didn't seem to notice or want to have pics done, she took about 30 pictures of our family! So fun! We did get the desserts first, then the pictures. We had a great table right on the rail (I made the reservations on the first day I could at 180 days +10). I think your family will enjoy it!
The only issues we had were that it starts so late, but we did it our first night since we live in Texas and at least on that night it would "feel" an hour earlier to my kids. As well, the bathroom is outside of the designated Dessert party area. If you are potty traning, it can be a bit of a walk. The bathroom was tiny, several kids had had accidents on the floor, and the paper towels were out. That was the only real downer of the experience. Not sure if there are other bathrooms, but this was on the Tomorrowland Terrace area, and that is where the CM told us was the closest.