And I have plenty of time to practice.
Check out Craigs List.
My dad at about 70 or so acquired a digital piano and resumed trying to play proficiently. He actually loved it and spent many hours at his keyboard
“Speaking of musical instruments, I have been thinking about getting a digital piano. I played as a kid and miss it.
And I have plenty of time to practice.”
Tell you what... You should! It will help preserve what you have left going forward... I know it is helping me. :)
I play and find huge advantages in it. Been playing all my life and I am pretty accomplished. What I find mentally exercising is improvising. It incites the creative brain cells one normally does not use but the whole benefits from it. It can also be very spiritual and can increase mental awareness and reduce stress.
Someone once told me that they were having trouble staying awake at work after a heavy lunch and she was at her wits end how to fix it. So I suggested do some light exercise after lunch to raise her metabolism. She thanked me for changing her life because it worked so well. Point is like you say, exercise it and it will serve you better overall.
Have you considered just getting a MIDI Keyboard to start with? Just plug it in your computer and download some good software and go. Maybe just add or connect to a sound system for fuller sound? There is some incredible software out there now! The sampling tech is now so rich you can truly make it sound like a Grand Piano or a huge Tabernacle Organ. And you can add layers of backup rhythms, guitars, strings, horns, drum tracks, Etc. All from the keyboard and cheap!
I like THAT kind of tech... lol :)