rogerc,
Stonyford is a great place to ride. It really depends on when in April you going up?? In early April, it can still be damp and chilly in the mountains, but by late April, it can tend to get dusty..
There should be plenty of snow now, but by April....who knows.....only mother nature..
The trails a Stony are a bit more advanced than other Nor.Cal riding areas...But still would not be a problem for you and your boys. You can get trail maps at the ranger station in Stonyford.
Next month were getting together for a ride up at Elkins Flat.
Elkins Flat trails are a little eaiser than Stonyford, in terms of novice riders.
Checkout this thread.
http://dirtrider.net/forums3/showthread.php?threadid=38085 for more info on Elkins Flat.
Rick