Definitely crib tents--they might still stay up and bounce around but they can't get out. The one I had to use a crib tent with still got out so I had to safety pin the zipper closed.

The diaper thing I had a problem with at naptime. I tried duct tape but he still got that off---I hear some people have had success. Also cutting the feet off a sleeper, putting it on backwards and safety pinning the zipper shut. I never was successful keeping him out of his diaper--I used to safety pin his shirt to his pants and he would rip holes in his clothes getting them off. If they want to get that poop they will find a way.