I have a Moby and a Beco Butterfly 2 that I used with DD. I wore her hands-free, but always had a hand to adjust her. When I take DD to the park, etc. she often needs to be wrangled. She resists, and I can just imagine dumping the newborn or her accidentally punching him. The alternative would be to leave the newborn in the stroller and listen for him while I chase M around and carry her back to the stroller radius if she got too far. What is a good stroller radius?