I’ve had the same problem with being unable to expand the bounding box in Illustrator. When I apply a drop shadow or some other effect and then place the graphic in InDesign, the edge is cut off a very little bit.
I solved this in two ways. One is to add little no color boxes beyond the edge of the image in illustrator. This expand the bounding box. The other is to place it in InDesign and expand the bounding box there.