There isn't much you can do about clothing for Ben unless you are skilled at modeling or clothing conversion from another model.  The only children's models that I recall that have underwear are DAZ3D's Kids 4.  I see that they are currently running a sale.  Otherwise, you are stuck.  The comforter is a prop with geometry.  It has no controls.  You might run a cloth simulation with it to determine if the draping will work.  If it doesn't, you will need to substitute a cloth plane for it.