hmmmm, FMQ slowly should give you shorter stitches, not longer.
if you aren't comfortable with FMQ, just do some curvy lines below the catepillar to look like movement and same with butterfly. or echo around them. just something to fill in the background of those large blocks. STID or 1/4 inch stitching around the others should work fine. good luck. cute quilt! just take it slow and go for it.