How young is to young for a concert?

My 2nd grade son is a huge fall out boy fan. They are coming close to us in April and my husband and I really were considering going. My son is angry and really wants to go. It is a 5PM concert, but only floor tickets are available. I know he would appreciate it, but I worry the crowd will be to mature for him. I want to be a responsible parent, but at the same time I really want to give my son this chance to see a group he absolutely loves. Would it be distasteful and irresponsible to take him? I remember going to see Tiffanany in 5th grade and I did not feel to young. Is this any differnent than taking a young girl to go see miley sirus?