I am in my 50's and DH is early 60's. We are not "old," but were one of the oldest couples on PIB after 10 pm. That being said, we had a great time people watching, but had had enough of the 20's crowd by that time and we were ready to head to the mainland to our hotel room. We are energetic, and still like to have a good time, and find Amish Country a little boring, although my Mom likes to shop there. Why is it that everyone assumes that once you hit 50, you don't like to enjoy yourself? We do just as much as when younger, just not as crazy!
That being said, my parents who like to have a good time and are not prudish by any means, would not enjoy the mostly 20's scene after dark on PIB, but would like the area.
I would recommend a nice hotel on the mainland and do a day trip to PIB, rent a golf cart, have lunch, dinner, and another day trip to Kelleys Island, again rent a golf cart - it is pretty spread out, and enjoy the scenery there. There is also Marblehead to see the lighthouse and a nice little park (not much else there). There is also a nice upscale restaurant at the Mon Ami Winery in the area.
Just some suggestions...Unfortuntately the Ohio Boards are not frequented enough, so try to contribute when I can.