I remember reading in a children's magazine or book (can't remember the name) that foot preference is established before hand preference. So, if you give the child a ball to kick, they will kick the ball with their dominant leg. I tried it on DD when she was switching hands and actually using her left more. She consistently used her right foot and now at 3 she is using her right hand for writing, drawing etc.
So it worked for me but I haven't tested the theory on any other kids.
“Live a good life. If there are gods and they are just, then they will not care how devout you have been, but will welcome you based on the virtues you have lived by. If there are gods, but unjust, then you should not want to worship them. If there are no gods, then you will be gone, but will have lived a noble life that will live on in the memories of your loved ones.”
― Marcus Aurelius