Some details should never be shared
I understand exactly what is going on. While I will encourage you to hire an attorney for legal advice with regards to divorce, but before you do that, please do NOT tell your husband what happened. That can be used against you by your husband in divorce court and it can affect whether you can get custody of your kids and if you will get any share of the property.
In addition to that, having a child from another man will completely change your life, because now your husband can divorce you or start mistreating you for committing adultery. Even if the child’s father wants the baby, it will do no good to your life because you will be forced to deal with two men even if you become a single mom.
Options after abortion
Abortion is not an easy decision for any woman and personally I have no opinion on it, but looking at the facts of your case, an abortion maybe in everybody’s best interest. If you do choose that path, pretend it never happened and this incident should NEVER be told to anyone.
If you choose to have an abortion, you should still continue with your divorce because it appears to me that you do not even want to try to make it work. You have not told me about how you will live, but I hope you have given some thought to being a single mom with such small kids. I wouldn’t say it is going to be easy, but you are not the first woman to go through this. Most women do just fine.
Options if you have the baby
If you decide to give birth to the child, of course, your husband will most likely divorce you, but you can give away your baby for adoption, and try to raise the other kids. I am also hoping that eventually after enjoying a few years of being single, you can find love again and remarry.