For the latter part of the trip I would recommend getting to Golspie early on the Thursday and doing a couple of runs (one to get your eye in) and then head over and ride the black trail at Balblair (techy XC). You could then head over to Torridon and camp/bunkhouse/hotel for the night.
For the Friday do the big Torridon circuit in Kenny Wilson's book (Coulags, Bealach na Lice, Torridon and Coire Lair).
For Saturday there are a few shorter rides in the area that would take a morning, giving you plenty of time to head south.
If you search this forum for Torridon and StuartieC you will find plenty of info and pics of the riding around Torridon.