It's a tough call.  If your lawyer goes after her aggressively in a courtroom a judge could have the perception that people are just ganging up on poor little BM.. who is only doing wht is best for her children in a very difficult situation with that mean old EX and his new wife who is so mean to her and her little babies.

If your lawyer avoids showing real evidence of her causing problems.. the judge can't tell her to knock it off either.

I honestly think the best focus is to not try to point out the problems that the other person is causing.. but focusing most on how your husband is doing HIS best to be the best father for his kids.. advocating for health care needs etc..

There have been a lot of people who have come on here and wanted to have their SO's ex nailed in court for all manner of things that were "annoying".. and in many cases not real proven or relevant issues.  

The court's main concern will be the well being of the children in these cases... and your DH's lawyer can ask for modifications like mandatory use of OFW to make communication consistent and on-topic... reasonable limits on interference with dad's time... even reasonable extra curricular activity limitations.  

But I think it's fair to say that your lawyer should know the particular judge you will be facing.. and what to expect.. where that judge's sympathies and interests may lie.  I wouldn't want to force a situation where it looks like you are all ganging up on her.. even though in reality it seems to be the opposite case.

We "played it cool".  It's a long story.  DH and Satan were already divorced before we met.  DH had to go back to change custody.  DH's lawyer is actually a pretty nice guy, money doesn't matter to him because he's just an employee of the firm, paid a salary.  He didn't hate Satan, just thought she was irrational, mental, and a poor parent.  So he was never a "shark", more kinda monotone and chill.  But Satan is an assh0le, and the courts here are fair and balanced, so she buried herself.

https://samvak.tripod.com/narcissistincourt.html

In the years leading up to trial, we refused to argue with Satan, ignored her most of the time.  That drove her nuts.  I selectively baited her into showing her ass, several times.  I also covertly provoked her.  I did some bad and illegal things.  Let's just say I exposed some of her fraud to Mealticket's family, publically exposed other things she did, targeted very few emails "from DH" to provoke rageful responses from her.  It drove her [more] insane.  I still torment her occasionally.  She's a serial killer, so if I disappear, you'll know why. 

You have to know when to hold them, when to fold them, when to walk away, when to run.  Naricssists have many weaknesses, which are easy to expoit.  You can play their own game against them.  Expose them, gossip about them, gaslight them, lie, feign ignorance, videotape them, refuse to comply with their demands, stare at them, taunt them, smile menacingly at them.  Throw social norms in the trash.  But when needed, be classy, calm, and angelic.

One piece of evidence was her phone records.  She called DH an average of 4x/day, for months, to threaten and belittle him, then went nuts, by text, when he reported her for harassment, and vindictively interferred with his visitation.  She got the police called on her a few times.  Her texts and emails were abusive and incriminating.  Medical records and attendance records proved neglect.  We subpeonaed the school and got a copy of a truancy letter the school had sent Satan that she'd kept secret from DH.  Proof of parental alienation, mostly by her own attitude and testimony.  It was obvious she coached Killjoy to hate her father, in fact Satan got caught listening at the door when the GAL interviewed Killjoy.  Then she got caught lying about that, and so many other things.

She joined the PTA at Killjoy's school, and only went to one meeting.  According to the meeting minutes, she only showed up to correct them on the spelling of her name, then she never attended again.  LOL.  We downloaded the meeting minutes.

She had to admit to being a highschool dropout.

She got caught doctor shopping to cover up things she was doing to undermine Killjoy's health.  The doctors saga, she admitted to taking Killjoy to a half dozen when she didn't like their diagnosis.  This is partly where I baited the emails in which admitted she wasn't following doctor's orders, but was mystified why Killjoy was sick.  We didn't even get to use everything in the medical records.  They indicated that she threatened the doctors, but we didn't even need to drag them into it.

She joyfully shared the litany of diseases she has.  Her favorite subject.  Phantom complaints that are all expected to be fatal.  She admitted she'd lied to DH and his family about having cancer.  MIL was present, so Satan was afraid she'd be called as a witness.

She bragged that she didn't work because she didn't "need to".  She smugly explained, between CS and Mealticket's income, she didn't have to work.  You know, because she's so desirable, men would line up to take care of her.  But then, she admitted Mealticket's kids were sleeping on the floors for his weekends.  We didn't mention this but, Mealticket was selling his plasma once or twice a month for cash, in addition to working fulltime.  Satan and Mealticket weren't married, we were.  We didn't bring it up, but I suspect Satan was having Killjoy call Mealticket "Dad" at some point.

Much earlier in the process, as an excuse for not working, she'd produced a document for the GAL where a doctor listed the medications she was taking for all her fake illnesses.  Fentanyl, methadone, etc.  Then she was uber pissed that the GAL shared that with the court.  She sprang out of her seat and shouted, "THAT WAS PRIVATE!!!!!!!"

LOL.  Oh, so much fun.

She tried to allege that DH is a monster.  He's got a degree in STEM, has been at his profession for more than 20 years, has zero criminal record, and is as docile as can be.  And their divorce decree doesn't have even a hint of domestic violence in it.  He'd given her custody and more than the legally required CS, plus so many extras.  She'd not wanted DH to find out she had moved in with Mealticket, who she'd been cheating with for over a year, at the time of the divorce.  But now she thought she could go back for alimony, now that she'd gotten what she wanted and he'd pissed her off, but the decree barred them from alimony.

Your lawyer should ask your BM questions that reveal her hatred of DH.  Then ask her if she tells the kids that.  Many times they will say sh!t like, "I have to tell them how evil he is, so they will be safe from him."  or "The kids hate their Dad".  Why?  How do they know he did X?  That's not true, why do they think that?

I'm not sure this matters but, I've always wanted to ask her how much money would satisfy her.

Your BM is smart, like the one here. She frames her abuse around what's best for the kids rather than personal attacks. It will be harder for you to trip her up because of that. 
 

Your DH needs to stop sharing anything. Why does she know you are planning something with your family? He should have just said,"we have a vacation planned for that week out of town" and let it go. 

We went for blood.  It worked great.  Any time they twitched out of line with the CO we smacked them with it.

They tried the manipulation thing, but , they had neither the brains, the stones, the resources, nor the time to pull it off.

As for not wanting the BM in jail.  If she is doing things that warrant jail time then jail is exactly where you should want her.  The only antidote to manipulation a d lies is the facts and "mom is a lying jail bird" is about as powerful a fact that there is in countering manipulation.

We buried the opposition in facts.  When we went to court we had it all well organized and documented.  They usually had little more than a few scraps of paper.  We would make our case, they would whine and cry that we were lying, BOOM, we would smack them with proof that they were the ones lying..... lather...... rinse....... repeat.

We won, they lost.  Even batting 1000 I have never left a family law court feeling like I did not need a hitgh pressure scalding hot shower to blast the skeevy feeling off of my body.

Full disclosure, we were the CP side of the blended family equation.