You didn't say when your trip was scheduled. We always have to travel during school breaks so summer is the best time for us to go BUT the crowds are big. We waited to take our boys until last summer at 11 and 9 years old. That place is so big with multiple floors that we felt it was too stressful for us to try to keep up with two over excited "little" kids in that big building while fighting the summer crowds of vacations in the past.
At the ages they were last summer, even if they got mixed in with the tons of teens and big kids ( there are plenty of little ones running around too ) we could rest assured that they wouldn't panic or become victims of any "bad" person. We got to play and have fun too since we didn't have to hover over the boys.
If I only had one to take, I would probably have taken him at at younger age. We are from Atlanta and have learned that there are a bunch of mean people out there so we tend to hover at times.
HTH and by the way,- we had to bargan to get the scamps out of there after 5 hours straight of games! It really can be a fun place to spend an afternoon.