I have a raised garden 24" deep and bound on 4 sides 10 x 4, length and width, bottom is clay and yard grass.  Will the trees stay in the garden layer or will they hopefully go to ground?  

The roots will work their way through the shallow part of the clay soil and spread that way. Think of the setup initially as a self irrigating pot.
I would not want the trees to be bound on all four sides unless the edges of the raised garden are shallow themselves, allowing the roots to keep going past the boundary, otherwise it'll be as if you planted your trees in a barrel and the roots will stop spreading at some point. This is not going to happen immediately, but two or three years (perhaps longer) down the road you might end up losing your tree if it becomes root bound.

It will greatly help if you break-up the layer of grass. If your raised bed is already full of dirt, take a post hole digger and open some holes through that layer for the roots to go into quickly. This will keep your tree from doing the lazy thing and keeping all its roots up in the raised bed.

Hi Sonnya,
24*40*4 all in '' ? 4'' is not enough ... 4' would be better LOL ...
If the spot is sunny the roots will get cooked in a 4'' area.