I loved that they had LEGOs perfect for every age, from large Duplos that little bits (almost 1 year old now!) enjoyed moving from place to place, to LEGO Juniors that were right up the alley for my 3 year old's interests and building capability. For the older kids they had every type of LEGO you could imagine, Princess, Fairy, Star Wars in addition to battle zones where families competed to win LEGO prizes. The older kids could enjoy Master Builder sessions where they could hone their creativity and building techniques.
Our kids moved from booth to booth and loved posing with the giant LEGO creations. My husband and I were particularly impressed with Super Man's multi-dimensional cape. My younger two were a little young to enjoy all the booths that were available, but we participated in the creation nation where E made a LEGO creation to be included in the US map and received a LEGO Builder gift for participating. He also got artsy in the Art Gallery which housed participants LEGO arts of work on large canvas like displays.
We wore little bits in a carrier, but many people had strollers and it seemed maneuverable. I packed water bottles for the family, which was a good move because it was very dry in the convention center. I also brought snacks because it was right during dinner and my kids are picky eaters. My kids couldn't participate in every activity, although the older kid events looked like SO much fun. I think the best age for the festival would be 6-14. As a child I was always a LEGO enthusiast, and this type of festival would have blown. my. mind.
If LEGO KidsFest is coming to your city, it's a must experience. But buy quickly, because all 3 sessions in Charlotte sold out two weeks prior to the event.