Be sure to say "Howdy" in the 50+ forum.
I started riding in about March, 1998, and on June 15th, 1998, did a week-long 350 mile ride, "Ride the Rockies" over Colorado mtn passes - on a mtn bike, yet!
And lots of other 50+ folks have done similar (and much more challenging) things.
Here is a pic of me on that ride at 58yo
So, don't let age get in your way of having a great time!