you'll need to take the initiative of getting them started in sports and encouraging them, then let the love of the sport take over. They won't come to you and ask you to sign them up for anything.
We certainly didn't force anything on our kids, but we don't allow electronics unless certain things are done. That includes playing musical instruments, doing chores, and playing a sport or having a hobby.
Sports provide structure, and a means to see progression in something due to the work you put into it. Progress is measurable, so they can become very gratifying for children. Add to that the fact that it helps them learn to deal with adversity and you can see why many of our leaders have been athletes.