BIGGEST TIP: Get to the Backyard Barbecue EARLY.
Here are my thoughts on the BBQ (from a review I posted on allearsnet.com):
My wife and I took our two kids (ages 4 and 2.5) on September 27 and it was a big highlight of our trip. The food and entertainment were great and the kids had a ton of character interaction. This event is very well run and very high energy. We were told to arrive early and I am glad that we did. I would suggest arriving before the listed start time and to allow plenty of travel time. Because we arrived early we had a great seat. It is important to note that the seating is first-come-first-served at large picnic tables. My wife and I were hesitant about the event after reading some lukewarm reviews, but were very pleased.
It is also important to note that this set-up is different from other character meals we have attended. The difference is that the characters do not have a specific set aside photo opportunity, nor do they make their rounds to the different tables. Instead, they come out and dance with everyone on the dance floor. This makes it much more incumbent upon attendees to seek the characters. Our kids had no problem with this and enjoyed every minute of dancing, along with many other children, with the various characters. We did the backyard barbecue on the final night of our trip and I think that this proved to be helpful because our kids were rather comfortable with the characters by this point. However, had this been our first night, the kids would have been much more timid.
I believe that a pretty good frame of reference for this event might be a large wedding reception (meaning a buffet, dancing and if you want speak to the bride you need to take some initiative). If your kids do well in this type of setting, they would do well at the backyard barbecue. This character experience is also different because the characters were rather active, especially Goofy who can really cut a rug!
We also found the food to be quite good. Early in our trip we had some bad barbecue chicken and ribs at Cosmic Ray's Starlight Café in Tomorrowland and were concerned that this was what we would get at the backyard barbecue. However, not to fear, the food at the backyard barbecue was far better (and I am pretty picky on barbecue). The drink selection, including beer and wine, was also good and the kids loved the Mickey Ice cream bars for dessert.