Just swing your club and see if they get interested.
Children are great mimics.
They really mimic adults. They don't have a concept of a golf swing necessarily, but if you can just show a nice, complete full golf swing, that's when they begin to get the mental picture. The parent doesn't need to be a good golfer. Just make nice golf swings, and that will give the youngster the idea. Quite honestly at this point the child is just concerned with hitting the ball and watching it travel.