Seller wants to stay on as GM -- thoughts/guidance?

I'm exploring a business -- mix of appliance sales, installation and service -- that has two sellers who started the business around 20 years ago. One is 70, not involved in the business, and very ready to move on. The other, who runs the business today, is 55 and wants to stay on as GM. He's not interested in keeping equity at this point in his life but wants to work for/manage the business for years to come. He likes the day-to-day and the team and the customers, but doesn't want to make big picture calls or set strategy. His son-in-law is on the sales team is a potential successor GM in the future. Has anyone kept on a seller as GM? How did it go? The kind of changes I'd like to make to the business to grow it are things that they know they need but haven't focused on -- a modern website, social media, digital marketing, and up-to-date crm/estimating/scheduling software. I'm not interested in running the business operationally day-in and day-out so in some ways having the seller stay on would be ideal, but I can see where it could be complicated emotionally or relationally given he would no longer be an owner.