Im not going to be much help, others will have more useful advice. But to get the ball rolling I will start with I’m not sure how old the kids are but it appears they have possibly been manipulated by bio mum, who may have resorted to dirty tactics, to get her kids back. 

Im very sorry you have had to go through this. It can’t be very nice. The court system appears to have seen through these tactics. 

Im not going to be much help, others will have more useful advice. But to get the ball rolling I will start with I’m not sure how old the kids are but it appears they have possibly been manipulated by bio mum, who may have resorted to dirty tactics, to get her kids back. 

Im very sorry you have had to go through this. It can’t be very nice. The court system appears to have seen through these tactics. 

Oh, this is hard - how old are the kids? How much custody time do DH and BM have?

Look up parental alienation, for starters.  But yes, I've been there, my SS lied repeatedly to help BM get custody. It's hard. You have to watch every word you say around them and be very cautious about what they can see in your house (private papers, etc).

Do they have a therapist? 

People who respect people don’t talk about them behind there backs,  This is up to your DH to parent his kids and teach them respect 

First of all, I know that it's hard to not be upset about the things that got brought up in court "out of context".

Those kids are old enough to understand that everything that happens or is said at one home doesn't automatically become something that has to be repeated at the other home.  We explained it to the girls that their mother deserved to have the privacy of HER home.. and we expected the same consideration.  We also said that there is a difference between hiding things from one parent and not "oversharing" every word.  Obviously, we would never want them to keep anything important from either parent, but that we don't have to hear everything that came out of their mother's mouth either.. and vice versa.

So, that is a general discussion that your DH should be having with his kids.. basically teaching them "discretion"...  

Also, it does sound like their mother may have made it sound like disney and rainbows so that the kids would want to stay with her.. and then pumped them for information.  The kids do need to understand that it was hurtful to you both to have things that were not meant with any bad intent used that way in court. 

Some of the discussion also needs to address the fact that the kids may be disappointed in the outcome.  They didn't get what they want... they don't want mommy to be sad etc.. It's ok for them to have empathy for their mother.. but they should also know their FATHER is happy that they are there and that the JUDGE decided that daddy's house was the best place for them right now. 

I would really try to not be too terribly hard on them though because it was most clearly their mom that was pushing all this.. and put them in this position..encouraging them to give her information.

I mean, they wanted their mother's love and affection.. giving her info?  that got them praise from her.. you can see how it would be hard for a kid to not spill beans.

For you and your DH... you may need to be just a bit more careful about your words around the kids.  Yeah.. it sucks.. but obviously mom has a way of getting them to talk.. so the best defense is to have said nothing at all that could be misconstrued.  Sure.. you were kidding..and the judge obviously saw that.. but I would still be mindful of little pitchers and their big ears/mouths.

If you had a lawyer they should have spoken up to explain that what was said was in a joking manner. While yes it's true you said it that is not the whole truth. It's like the nickname I have for SO's oldest. It's not cute and sweet and some who hear it would missunderstand but the child understands my intent and she actally likes it. It's not vulger but I do have to explain it.

No, you don't walk on eggshells around the Skids.  Site them down, read the ruling to them, explain that they do not get the choice to live with BM, that it was the Judge's decision... then roll our the court transcript and go through each and every question posed by the BM's attorney that clearly came from the Skids and was twisted by the BM's attorney.

Then outline how htey will not be included in any significant conversations until they can be trusted.  Keep a daily journal so that you can refer to it when they or BM pull this shit again.

We were fortunate. SS was a sharp kid who understood when we were joking with him or teasing him or each other.  The toxic crap came home with hom following a SpermClan visitation.  It was not joking. They were manipulative, guilt card playing, toxic assholes.  We are the ones that called them on their bullshit n court when they forced our hand with their toxic crap.

I struggle with wanting to tell my skids to shut their f****** faces around their toxic cunt of a mother.  I want to yell at them to not tell her a damn thing about me or my life or my kids or my interests because she will try to use every last thing that she can against me.

But alas, I can't tell them this.  So I just have to bite my tongue.

The funny thing is she screams constantly. But I feel like I'm walking on eggshells every time they're over. Anytime I raise my voice they're going to go home and say how I yell. It's ridiculous.