If you head to Ripley, you could carry on northwards to Fountains Abbey (out of Ripley on the B6165 towards Pateley Bridge, then first right signposted Fountains Abbey)
That will take you onto the Way of the Roses cycle route (NCN 688) to Fountains Abbey at the end of Watergate Road.
You could then continue along NCN 688 through Studley Royal deer park (through the back gate, pedestrians and cycles only) and on through Ripon. The return to Harrogate can be through Littlethorpe, past Bishop Monkton and Burton Leonard to Knaresborough.
The last bit to Harrogate can be along the Beryl Burton Cycleway (turn right immediately after the A59 bridge over the River Nidd in Knaresborough, opposite the entrance to Mother Shipton's Cave)
Cafes are available at: Ripley Castle, Fountains Abbey Visitor Centre, Ripon City Centre, and Knaresborough Town Centre.
A quick "rough and ready" plot of this route in RwGPS gives a distance of 48km (starts and finishes at Harrogate Railway Station (East Parade side)) and approximately 400m climbing.
Hope this gives you a rough idea of a route.
Edit:
https://ridewithgps.com/routes/46281562 is the rough plot, feel free to borrow and adapt as you wish.