I think 3 1/2 is way too young for an indoor concert. We started taking our twins to outdoor venues at around the age of 4. Their first concert was the VH1 barbeque with the B-52's and they loved it! It was outside, and they could run around, though. That helped alot. They are 11 now, and only one has the same musical interest as I do. She has seen Springsteen several times and is going to her 2nd FM concert (if I can get "good" seats!) at the end of the month. She is very good natured, knows all the songs, and would rather pee her pants than leave in the middle of a song!
Her sister, however, I probably wouldn't take to an indoor arena yet, because she gets bored easily, and would be distracting to those around her - a big no-no in my book. I would tell your child that this concert is for adults, and take her to The Wiggles when they do a show in your town.
Eileen