I know I will take the blame for this and be publicly portrayed as worst daughter ever. (seriously)
I know if I rolled over and went I would forever live with having been finally 'brought under control'.
OK, so go with what you know....
You KNOW they won't like you NOT behaving, and you know they'll bad mouth you. You have NOTHING to lose here then, do you?
what you have to work out here is WHY their opinion of you matters, when no matter what you do/say/are/are not makes no difference whatsoever.
Can you picture yourself as you are now?, all tense, frightened and worried? shoulders tensed? back stiff? legs and arms? Tight knot in your tummy? feeling sick with fear?
yes?
Now look at why you are feeling like this. THEY are making YOU feel like this because THEY want you to. It makes them HAPPY to know you feel like this.
On the other hand...Your DH knows they are wrong, you too know they are wrong..
NOW!...
Let go. just let go. know that you are doing the right thing, that your H supports you and the children will be fine. Know that YOU will be OK.
Why will you be ok? because you were OK before they started guilting you, and the only difference in how you felt before and now is the fact that these shitty people who want you to be unhappy have made you feel bad.
You have done all you can. You have left doors open, and are placing trust in those that you hope will understand. Whether they do respond you as you hope or not is THEIR choice, nothing you can do to make them do what you would like them to do. Now is the time to let go and let them be the people they want to be.
Remember that those who mind don't matter, and those that matter don't mind.