Hate the IN-Laws

I don't know what to do. Me and my husband have been married for almost 5 years. My husband didn't talk to his father for 2 years before we got together and I got them to start speaking b4 we got married. I regret it. My father in-law and his wife have my husband so screwed up on what a parent should be. They constantly put his mother down in front of him. His mother left the whole situation with him drinking and things after 23 years. He went straight to bed with a "friend" of hers that night. The now step mother threw my husband out while he was still in highschool and ready to graduate in a few months just because she didn't want him there they wanted to move. His father did nothing. So that is why they didn't talk. So to the point they begged us to move near them so we did. We bought our house and after about a year they started not coming around. His step mother is so dirty and strange and embarassing to be around. His father is acting the same way for the past few years. Now that we have kids I don't want them in our lives any more. They constantly try to come between my husband and his sister. Once my 1st child was born they came around non stop for the first couple months cause they were gonna change and blah blah. Then they backed off. Now I grew up with grandparents never around other than when it was conveinient for them. I don't want my kids going through that kind of hurt. They use the words "getting my fix in" now when they do see them and then say "that should last for awile". So I finally told them off and how I felt and told them till they decide to change for good to never come around again. My kids will grow up not knowing them. So now they are back to playing my husband and his sister back and forth. They never bother with my sister in law unless we don't speak to them. It's like they can only like one at a time. So now she is kinda in the middle but getting what she wants from them. "attention" I feel she has longed for from her dad, but I don't think she can admit that. I feel so bad cause they have done this before when we didn't speak to them and she has 2 kids involved. I feel so bad for her 2 kids cause they her dad is sucking to them and doing extra things never done before and we know it's not gonna last. She insist she understands that but still subjects her kids to it and they are the ones that are going to have her heart broken in the long run when he stops bothering again for something better that comes along. How do I handle this from here. I don't want to fight with his sister cause we actually get along, but I know she is setting herself up for failure with them. I also don't know what to do cause it hurts my husband his father is never around when needed, but he LETS his wife control his life and he just doesn't care. I want to sell the house and move, but not sure what else to do since they obviously act like 5 year olds and will never grow up. Where should we go from here??