If the stones are heavy enough and you're able to grip them, you can do some loaded carries Strongman style!!!!!!! Killer cardio hammers the back muscles and posterior chain too.
EliteFTS was having a sale. I'd say order a dragging sled with straps. You can do 1000000 variations of things and could use the rocks for weights (I'd set them on a towel to prevent scratches and movement).
Just tossing out ideas! Trying to help you stay sane =)