If you're looking for tech singletrack and good freeride, then heading to BC is one of the obvious choices as you mention. You could do several days in the Nelson, Rossland or Fernie areas. Then head West towards Penticton/Kelowna or Kamloops and then further west to ride in Vancouver, Squamish, Whistler and Pemberton.
Personally, if I were doing that trip, I'd head to Nelson (4 or 5 days), 2 in Penticton or Kelowna (breaking up the drive) and the rest in Vancouver/Whistler. I've yet to ride Nelson (this summer it will happen), but everyone I know in Canada says Nelson is a must with burly XC (canuck style xc) and beautiful FR stuff. I warn you though that the riding up north will make you want to emigrate....
On the drive up, you could swing by a new resort in Idaho called Tamarack. They just started building trails the last year or two, but they may have more developed next year. It's not too far from the town of McCall, so it may be worth investigating. Also, there's Silver Mountain which is outside of Kellogg and they have lift accessed stuff in the summer as well.....
On another note, there's always Tahoe. You've got Northstar for lift accessed riding and some amazing trails and scenery all around the lake.