Thankfully, with age usually comes greater resources, so picking an appropriate “sidekick” for later years isn’t too prohibitively expensive.
Two handguns that have impressed me for older shooters are the FN FiveseveN, and the M&P 380 Shield EZ.
The FN is a full size, service quality handgun with a twenty shot magazine that is lighter when fully loaded than an empty Glock 17. It has almost no appreciable recoil, devastating bullet geometry, boringly consistent reliability, and a point blank range longer than any other handgun.
Despite complaints the 5.7x 28mm “armor piercing” ammunition it’s meant to fire is not available to the public (and thus negates any inherent advantage), law enforcement grade ammo sporting the same bullet geometry as the military round is easily available for use against un-armored opponents with the same devastating results as its military cousin.
New to market, but with an outstanding pedigree, is the M&P .380 EZ. This handgun was specifically designed for limited strength users with an eye toward overwhelming safety (i.e. serious female shooters and CCWs).The slide can be racked more easily than any other I’ve ever experienced. The four pound out-of-the-box trigger rivals, if not surpasses the Sig 320 recently adopted by US armed forces owing to its internal hammer rather than striker fired mechanics. It also has a grip safety as well as an optional frame mounted safety.
Were I choosing a handgun to teach serious shooting techniques to my wife or tween, this is the one I would pick.