My parents want to live close to me, I can't think of anything worse. Any advice?

My dad retired 5 years ago & told me that the day he did mum told him it's now his turn to look after her. He does everything for her. Cook, clean, shop, cups of tea. 4 years ago dad attempted suicide & I see now that mum has attributed to this. He won't leave her because he loves her. She wants them to move 14 hours away to live in my town so they can be close to my son & me. My mum is so so bitter. I am the only child out of 5 who has talked to her in 20 years. Mum hates everyone, is so negative but sugar costs it or talks in codes around my 8 year old son - because I told her to stop. If dad dies there is no way mum could go out & pay bills or but food as she doesn't drive or walk or catch a bus - she's very anti social. I don't want this kind of life for my son & I. We are happy & having them living close would change our lives for the worse. I have told them that I don't know where I'll be in 10 years when my son leaves home. But by the next phone call she talks about moving up here again. She is very controlling & has been my whole life. Please help me. I don't know what to do. I'm only 45 and they're 67 & 70.