Oh Barbara, my heart and prayers go out to you!!! I know how incredibly hard this time is for you, but just know that you are doing the absolute best thing for your children in the long run!! As a child of a very messy divorce, I know how things get misconstrued (your husband may say alot of things, and try and get your kids on his side...and they may believe him at first, but when they get older and wiser, they will see the truth! Believe me on this one...)
You will be the good guy in the long run. Your kids will appreciate everything that you're doing for them, especially if you don't play the blaming game....it's hard enough having to go back and forth between parents without hearing criticism about each one from the other!
Best of luck Barbara! You are a very brave person and your sons are very lucky to have you looking out for them.