It definitely sounds like you considered all the angles on this issue.
So far, you've heard from natties such as Pwnisher, Shadow, and myself. And you've heard from guys who are open about using such as Reed and Flip.
I still believe that, once a lifter passes the newbie phase, some of us - especially the natties - simply must let those abs fade several months out of the year if we're to continue making gains in strength and lbm. We just can't use that as carte blanche to put on excessive chub. But that's where the discipline kicks in; this game ain't easy, as you already know.
Since you've got 20 years gym time with all the natural lbm you can attain, have goals which are more endurance-sports oriented (you mentioned running and swimming), and change in lifestyle (congrats on the child) - the decision has practically been made for you.
Take consistent measurements using the same method. Photos can certainly help. Keep a close eye on performance to make sure there aren't substantial drops (although some occasional regression is perfectly normal for any human being).
Once you pass the learning curve, you'll be able to locate that sweet spot in which performance is improving - or at least not suffering - and you're content with how you look and feel. In time, you should be able to adjust caloric intake to focus on one aspect or the other. Then, as priorties shift, you can make compensatory adjustments the other way.