Advice about MIL

Hey all! My in laws want to come down to be here when baby's born. We live 1000 miles away and I really wasn't planning for anyone to be here for the first few weeks so my husband, baby and I could establish ourselves as a new family, get to know each other, and get into our routine. So this is a new twist.. After discussing with hubby, who would like them to be here, we've come up with a plan to put them in a hotel nearby so we can still have our space, but they can still help. Good compromise right? Soo here's the issue. My MIL has a young child with no father around (in laws are divorced, but are good friends; she got pregnant a few years ago by a boyfriend then broke up with him, so he doesn't know his child and the child doesn't know who her father is.. Don't get me started on what I think about that!). My thing is, I don't want her kid around our newborn. I just don't. She's undisciplined, does whatever she wants, is extremely rough with our dogs, is loud and obnoxious. And gets away with it all. How do we tell his mother this?? I've tried to drop hints but feel it's not my place really. I've told hubby to ask if she will be able to line up a sitter on such short notice, but don't know if that will even get the message through. Any ideas on this one?