There are many ways by which your children could spend their free time. You could always encourage them in the different subjects in school. Or do some physical activities or socialization. The key here is to make sure that early on, they would have a healthy amount of different activities.
The academic stuff
School could be fun. If you have children in kindergarten, you could check out books that have relatively big fonts and colorful pictures. Also, you could gather different toys that are educational. Like toys that are related to counting. If your children are already in grade school, you could give them other reading materials. It could be related to their classes.
There are parents who let their children attend special classes. There are Kumon math classes. If you are living in a different country, you could also let your child learn either your language or the language of the country you are in. It depends on your situation. In any case, that is one practical consideration.
This is an important aspect of growing up. No one is an island. Even in kindergarten kids know that. With this in mind, you could encourage your children to play with others. It could be in the playground or at your own home. Observe them every once in a while when with other kids. There are times when you would see them having fun with others or maybe you might see them fight. Let them learn the value of friendship, how to make jokes and have nice clean fun.
Even the clumsiest children need to go out and play. Everyone needs that time. Let them play and learn. There are different kinds of sports like soccer. It is not always easy as they might hurt themselves. But you have to give them that. If you could, just let them be every once in a while. There might be times that you have to be the one there to hold them as they try to do the monkeybars or chase after cats. Usually it is the fathers who are expected to do that but moms are awesome too.