It depends where you live and if your child can speak German. I have a son at TSV Ost which is near
Rosenheimerplatz. They have a nice trainer for the 5-year-olds who is a tram driver, which the kids think is cool. Being at the football club also helps with learning Bavarian, but is quite multicultural at the same time. All in all a positive experience for teaching kids that there are all kinds of different people who come from all over the place.
It seems to me that sports/football clubs are two a penny in the suburbs but there are not too many in the city centre, due to space reasons. Another thing to take note of, is that training is usually twice a week and when they start playing in a league (from 6 onwards) there are lots of games on saturdays too. It'll take up a lot of your time, so it's worth picking somewhere local where you might be able to share the burden of bringing and fetching with others in your neighbourhood.