Same as any other business, kick them out for a number of years, then see if they still want to come back. The old guy in charge also needs to remember it will be a team effort for a while. There are very few businesses where one person makes all the major decisions. While Junior may make a bad decision, chances are just as good he will have a stroke of genius and think of something Pops never thought of. They both need to listen to each other and work together.
I come from a fammily business background. The business will probably close when the 2nd generation retires. There are members of the 3rd generation that work there, but none that want to take over. The perspective is very different once you have distanced yourself from it. We've all seen the outfits where Pops can't understand why the youngun decided to retire from being the hired man. You know, still the youngun at 65.