I'll give you a few experiences from my personal history.
When I disclosed to my teacher at school that my dad was sexually abusing me and was grooming my younger sister, school got social services involved and they mandated a "family counseling" session.
(This was back in the 80s so safeguarding was unknown and SS's primary objective was to stop families breaking up if at all possible.)
It was a preview of hell, from the victim's point of view. The entire hour was given over to the abuser spouting forth his feelings about how we were all colluding against him and that I was obviously angry with him because he'd said I wasn't getting an Atari 600 for Xmas and had brought up all these very trivial sexual assaults in order to punish him for that. I didn't speak. My sister didn't speak. My mum said some wishy washy crap. The mediator/counsellor was oozing sympathy for my dad. (To be fair he was a very skilled sociopath and fooled many with his charming surface.)
Secondly - as an adult. I was on the brink of leaving my H due to his attitude to DSS (his son, not mine, but we had sole residency and he addressed me as mum, I went to all parents evenings etc. Birth mum not in contact.) I arranged a family counselling session as a last ditch effort to try to keep us all together (I was very concerned that if I left he would deny me access to DSS and that DSS would be left with only an EA and VA dad.)
The counsellor was actually very good but it was a lost cause since my H would not engage with the process and just spent most of the session saying "I dunno" and "Ugh, whatever." My DSS found it awful.
Thirdly, I went to a group session with my then partner, my D(S)S (by this time I had been granted residence) and myself, with my DS's regular counsellor.
All of went in with an attitude that we wanted to bring some issues up which were upsetting us. Some of the things brought up were hard to hear, but all three of us were prepared to compromise, and to listen to the counsellor's suggestions, and it was actually very productive.
So I guess the takeaway messages are:
Never go to mediation/counselling with an abuser - they are far too adept at turning themselves into the victim
Mediation or counselling will only work if ALL the parties are prepared to make compromises, to apologise for past hurts, and committed to making things work TOGETHER.
Only you know if it is worth a chance for you. But good luck whatever you decide.