It isn't graded. I've just plotted the route on Garmin Connect, and it's all wide track with a bit of narrow thrown in. I can't see any technical stuff. MBR rated it medium, but that could be simply distance- I can't see any features that would raise it above blue. Don't worry about holding anyone up, that 's the whole point. We go at whatever pace it takes.
I've decided to go with the Bakewell route. It takes us south down the Monsal Trail, along paths and tracks to Rowsley Village, then North through Rowsley Wood to the stone circle above Beeley Plantation, then West to Calton Houses, up through Chatsworth Park to Edensor, and back down to Bakewell. Total 14 miles.
I'll see if I can work out how to link to the route from the Garmin site.