My oldest (almost 7) benefits from a bit of structure on the weekends rather than a free-for-all both days. He's also very active, so it works out well to have one sport per season. Like last spring he played baseball, soccer in the fall, tennis in the winter. Baseball and soccer required practice one evening per week. Also swim lessons once per week.

Just started swim lessons for our 4yo too. They sometimes say they want to do something like their older brother, but the couple times I've signed them up for an activity (something very casual, like Coach Doug), it's been a mixed bag. Will likely do soccer in the spring with their preschool buddies, but that's all I have planned for now. They are more content with the playground and such for now.

My 9 and 7 year old do two sports (tennis and swimming) twice a week (so 4 days) and language class on weekend. We don’t want anymore, but we will end up doing something else in the spring.
Our 3.5 year old plays soccer on Saturday. We will sign him up for swimming in a year, but the water is cold and he is super sensitive

Mine just turned 4 and is in full day daycare. we do fall soccer saturdays for 10 weeks and swimming in the spring for 8 weeks. Nothing else. Soccer we mainly do as a fun activity with her same age cousin and a reason to get out of the house.

Under age 5, I find that just going to farmers market, library, running errands, playground, nature center, etc. are PLENTY of stimulation on a weekend. And I would not want to add an activity on weekdays after a long day of daycare.

Kids this age do not need much. Their brains are wired to learn social skills and routines and so any mundane daily activity is actually very age appropriate- just participating in basic daily life