We ride a lot in Yosemite. We go every year and do 50 - 80 milers there.

I have ridden the road from Crane Flat down to the Valley. It is actually fine for an experienced rider because you get going faster than the traffic on the downhill sections (most of it!) and it is beautiful. Also on the short tunnel parts you're going downhill. However, I would not let my 10 year old ride it. There is no shoulder at all, and frankly I am more worried about her on a long sustained downhill than anything else!

Tioga Road has opened up. We were only able to ride about 30 miles out and back last year on it because it was closed. That is a tough-ish ride as it is pretty high and pretty hilly.

I love doing the ride from either Wawona or the uphill end of the Valley tunnel up to Glacier Point and back. The climbing is steady and nothing too steep (til the end) and it is a beautiful ride. I find that the tour busses are very considerate of cyclists, even though the road is relatively narrow.

Also riding from Wawona to the valley is a good ride - rolling and you hit that long tunnel on a downhill so you can take the road and not worry about cars. Again, I wouldn't want my 10 year old doing it unless we were on the tandem.

For a kid, the valley loop, though totally flat and a bit dull, would be perfect.