Sounds like Kenzi is very distressed. Is this her first litter?
The biting doesn't necessarily mean that she is trying to hurt them in any way. I think she wants to move them, and new moms often don't really know how to handle the kittens yet. I think it's okay to keep the kittens with mom in the nesting area, but you should continue to watch her to make sure she isn't trying to hurt them or what so ever. The heating pad is good, that should warm them up properly.
Is mom washing them and letting them drink now?
The biting doesn't necessarily mean that she is trying to hurt them in any way. I think she wants to move them, and new moms often don't really know how to handle the kittens yet. I think it's okay to keep the kittens with mom in the nesting area, but you should continue to watch her to make sure she isn't trying to hurt them or what so ever. The heating pad is good, that should warm them up properly.
Is mom washing them and letting them drink now?