I would stitch in the ditch everywhere then cross hatch the background of the elephant blocks, do a simple cable in the sashings and do charm tacks (Quiltmaker magazine term) in the cornerstones.
I'd also stitch diagonally through the 4-patch blocks in the border. Since this is going to a child and will be used and washed a lot, it will need a moderate amount of quilting to hold together over time.
Cute design--he will love it!