If you want to combine white-water paddling and mountain biking you might
want to check out the area around Folsome Lake and the South Fork of the
American River. This area is in Northern California near Placerville about a
2 hour drive east of the S.F. Bay area (1 hour east of Sacramento). I was up
there last week kayaking the river with my son and we brought the bikes
along to check out the local trails.
The river has a couple of fun class 3 runs divided by a class 2 run. All
are great for kayaking or rafting. The river feeds into Folsome Lake.
The Salmon Falls trail is a 9 mile single track that follows one shore of
the lake through the rolling foothills. It can be done as a 18 mile out and
back or a 9 mile shuttle run. It's relatively easy technically with about a
1000' gain/loss. There is a lot of campgrounds in the area. It's very hot
in the summer but there is the lake and river to swim in. There are other
trails in the area but I haven't ridden them yet.
This is a good spot for a family vacation especially if you have divergent
interests. The lake is also used for water skiing and jetskiing.

Pauly