Detective Conan, Tantei Team KZ Jiken Note Recommendations
Small children solving small mysteries! The Detective Boys episodes in Conan where the gang of three boys and one (sometimes two) girl(s) go around solving things is very similar to the set-up of Tantei Team. Conan deals with more crimes where in reality it would actually be deeply inappropriate for grade-schoolers to be meddling in though, like murders.
Both shows feature small children playing football/soccer.