If the piano is something that would make you happy, there is no doubt you should pursue it. There is no such thing as "too old" for any skill. With current technology, you can definitely talk to your children more. It might make you feel less lonely, reminding you of the days with a full house. I am sure your friends would understand your position and that you won't have to third wheel. Getting out more will increase your dopamine release and some fresh air will increase serotonin, along with less television. In general, you cant shut yourself out.