3 a bit young. At that age anything that begins muscle development is fine. A few general suggestions
1. Any sport the child enjoys that develops hand eye co-ordination is ideal.
2. The child will find his way to a sport he enjoys, support him.
3. Its fine to expose him to different sports, but try extra hard to not impose your own agenda.
I'm 76. At 12 I was 6'6. Of course all I heard was "basketball." Coaches, friends, my dad. I hated basketball, much preferred baseball and football. Pressure for kids is often counterproductive.
Let your kids find their own way. Good luck.