The C&O Canal towpath trail from Pittsburgh to Washington DC has the bed and breakfast options. I've never ridden it but I'm told nice things about the experience.
The NCR railtrail north of Baltimore runs from abbout 20 miles South of the MD/PA line up to York. So roughly 40 miles total, one way.
There isn't much to do a long the way though, at least on the Maryland side. No hotels, nor the need for them over that distance. Just a few trail side train related buildings. And a giant hill full of garden gnomes (words are inadequate). There is more stuff to see on the PA leg of the trail, but I'm not super familiar with it.