How about joining the National trust? There will be plenty of properties near you, and they are usually a low energy mellow visit, perhaps with a nice walk through the garden. They always have a nice cafe as well, with easy parking and provisions for kids. It's not all stately homes, there are factories and docks as well.
More importantly if you are alone , there are tons of volunteers who love to have a chat about whatever. It's not so awkward going somewhere by yourself if there's someone you can talk to like another human.
Our family has been members for years and we really get lots of use. Any time we are somewhere doing tourism and the original destination is closed, or it's raining or whatever, we can always open the app and find some interesting NT place nearby.