K.H.
Maybe a swim team would have all kids at the same time although some teams split up the big and little kids. Some families have one child play up in soccer or baseball but two years might be too much. Tae Kwon Do studios generally mix all ages and even adults can participate. Tennis also often splits kids by ability rather than age.
That said, I miss the days on the side lines with all three boys or chasing the smaller ones while watching the big kids play. But there were days when I hoped for rain because I literally couldn't get all three to their games without leaving someone stranded. And it gets harder when they are older because the local league starts playing leagues from farther away. And the boys would tell you that I mostly liked the chatting with other moms.
Good luck.