Sue, how about the Gaick pass as an anti-clockwise loop?
Start at the south end on the A9 by the northerly Trinafour junction, travel north on a mix of good estate roads and a short section of very sweet singletrack by the top loch. Continue north into Glen Tromie through to the Spey valley and then head west past the Ruthven barracks ruins. Overnight at Newtonmore, where the pub is very good.
Day two, ride west past Laggan Wolftrax (café) on the road, then head south at Ardverickie over to Loch Pattack, loop around past Ben Alder Lodge, east again to Dalwhinnie and back to the start on the Sustrans route near and beside the A9. You could do it on a CX bike but it would be more fun on an xc-ish hardtail. Highly recommended.