I really enjoy my job so don't want to retire early but it does mean I am tied to school holidays. If your children are grown up then presumably there is no reason why they couldn't sail with you on an adult only ship? If you had grandchildren you could go on the Celebrity ships that are newer and bigger.
To me, making at least a couple of their older ships adult only is a no brainer, as P&O do. We are not loyal to any particular line and will always shop around, largely looking at dates, then itinerary and price. Celebrity has 14 ships so making 2 of them adult only would barely make a difference to me, but could attract others to them. I think they are missing a trick.