I'd start with 10. As was said already, it's way better to add more than to have too much. You're also going to want to drive on it a bit and push it in. If it's too much to begin with you're going to make gravel ruts and such. I hate driving my car on drives with too much stone. You end up spinning wheels and tossing rocks.
Personally I'd probably put a layer of QP down then 3/4 blue stone or whatever. The QP packs hard but moves out easy so if you don't like it, it's easy to change by just raking it up. I guess it just depends on how your stone currently is. If it looks like mostly dirt, with grass everywhere, then a QP base will make it nice and level for adding the good stone on top. If it just needs thickened up, then by all means put more of the regular stone down.
Yards vs tonnage is getting my math messed up. 10 yards is about 25000lbs, I.e. 12.5 tons. $29/ton for 3/4" blue stone is a decent price. That's going to come out like $55/yard which is cheap.
Those big tri-axle dumps hold 14 or so yards, so no matter what, you're not getting it all(22yards) in one unless it's a tractor trailer. You'll probably get it in a 10 yard dump, which is what most places that sell stone use.