I took my two girls to their first football match when they were 7 and 9 respectively.
The older one enjoyed everything except the football, she was fascinated by the support staff, photo journalists and medical staff who drive the golf buggy on the pitch for serious player injuries. This is the Czech Fortuna Liga, btw.
The younger got bored, which was understandable as it's the Czech Fortuna Liga, but enjoyed the day out. The thing is, taking kids to a match here costs next to nothing, we ended up getting season tickets for them but pick and choose the matches we take them to.