Children growing up around the mentally ill?

I am a new mum. Before this baby I stayed with my husband and his family, i.e his mum, dad and sister. His sister is blind and suffers from psychotic depression. My MIL is also on anti-depressants, she does not go out, has no friends and no hobby, which I suspect is also slightly odd behavior. We stayed with his family because that seemed like the humane thing to do keeping in mind his sister's illness and his parents' helplessness. Now however I'm a little more concerned about the well-being of my son than humane treatment of my in-laws. Is it safe for my child if I continue to live with my in-laws considering one of them (not counting MIL) is mentally ill (though not violent) and shall remain so (or so her doctors say) or should we move out? Moving out is going to be tough on my DH, but if he absolutely has to do it, he will. So I don't want to ask him to do it unless absolutely required.