My future husband's mom is on drugs......

Ok so we're in love we're getting married and of course we want kids,, well the problem is my mom died when i wuz younger so my kids will only have one grandmother which happens to be on drugs really bad and my husband is always sad about it,, she's done alot of mean things to him growin up that he will never forget because she been on drugs for years,, but what do i do??? i dont want my kids to have an addicted grandmother u know?? do i leave the love my life when he hasnt done anything wrong or do i stay in a situation that i dont like or cant fix???