I'll see what I can come up with - a route out via Haxby, Wigginton and Shipton presents itself, so I'll run it through the routeamajig tonight and see what pops out. Unfortunately, when heading out towards Newton/Linton, the river tends to get in the way a bit. Also, the Haxby Road route has the advantage of the underpass below the A1237
As for a straight run back, that's easy - if there's enough light and it's not too wet then we can come back via the cycle-track by the river. Failing that, back roads to Overton and then the cycle-track by the A19 from Skelton, through Rawcliffe and back to the station. This is about 11 miles.
I'm mobile in the sense that I can push a 71" gear with minimal discomfort rather than gut-wrenching agony so providing I take things steady and not go haring off up hills(!) then I'll be fine.
EDIT: We have a possible route: York -> Haxby -> Strensall -> Sutton-on-the-Forest -> Huby -> Tollerton -> Newton-on-Ouse. 21 miles pretty much on the dot, and then back to York via the quasi-direct route. How's that?