you need to try and be very specific that you are asking for family therapy help (remembering that this does not need to include ex in the sessions at least initially) so that dds can have a future relationship with their father (everyone is very big on this idea...) [the fact they may or may not is irrelevant at this stage, phrase it as tho you really want things to improve, which you do in a way...if it is possible...]
go back to GP get re referred to CAMHS and if you get same adviser ask to speak to his supervisor instead.
keep telling ex you waiting for CAMHS support and family therapy and he will get invited.
there will be hopefully a branch of CAMHs that does specific family therapy work in these situations, make it clear this is what you looking for : to explore the dc concerns over contact and present it as you want to work to move forward. .
if ex then hears it from a therapist that he needs to do x or y he may listen...he certainly wont ever listen to you.
yes it does take some pushing to get the right response nd support from CAMHS (it took ages with dds, at one point i had stopped contact and ex was getting serious MH input from local adult MH services and GP/SS supported me in stopping contact...you not quite in that situation.
but when ex got "well" again it got back to being like your situation - an angry man who screamed and shouted and dd1 who didnt want to go at all. dd2 kinda wanted but had concerns also.
.
currently, dd1 16 does not see ex; dd14 does see ex ad hoc about once/twice per week - she arranges herself now;
oldest ds sees him also weekly.
your dc are young and you have many more years of this.
focus on getting them family therapy help, which would involve therapist working with them (you would likely sit in) then maybe bringing ex in as well, also they would talk to ex and hopefully help him see things and improve... this would be over many months and is your best way forward.
meantime stop contact.
don't put dd thru this.
let her have some time away from him.
if she was same about going to school you would work to get to the bottom of what was bothering her. and that might mean stepping back, holding off then gradually with support building up on her terms.