Don't let the situation turn into a competition between you and the OW, TAL. And don't let her have "power" over you...do NOT ever allow her to make you feel that you aren't "good" enough.
All that glitters is NOT gold; and your children will see through all of it, in time, as the new will wear off...and what's underneath won't be all that it seems.
This will come in time.
I have not dealt with what you're talking about; but I know that as a mother, you've done all you can do for your children; and you won't "lose" your children to OW.
Children need MORE than material things; they need a shoulder to lean upon when times get hard, they need love and understanding when they need it, and they need to have someone to count on.
You ARE that someone; you are their MOTHER; and NOTHING will EVER take that away from you.
You are a rock for your children, stronger than you will ever take credit for. In spite of all of the mistakes you've beaten yourself up for, you have BEEN THERE for your children; and in many ways, you will always be there.
You've given them MORE than your husband will ever think about giving them; he abandoned them, you did NOT.
Give yourself MORE credit for being who you are; and for the strength you have shown in such a terrible situation that has gone on for SO long.
Above all, hold your head up high; you did NOT commit adultery, your husband did.
You are in a better place than he will ever be in; you retain your integrity, honesty; and you are guilt free...he is NOT.
Just a few words of encouragement; you're handling the situation the best way you know how; and you're doing fine.
Much love,
HB