detect collision with child objects
 

If a parent 3d node has several child objects, how can you detect a collision between a separate moving object and one of the child objects, and
how can you tell which child object was hit?

You could try using a method like the one used in the following knowledge base article for detecting collisions with individual bones of an avatar.

http://kb.worldviz.com/articles/350

Let me know if this is along the lines of what you are looking for.