Are you being represented at all? It is much easier for a barrister to say the ex is alienating the kids - (or attempting to) than for you to say it. If you say it, it's an allegation.
My tip is to describe the behaviours and let the court see they are alienating behaviours, without actually calling them that. And use alternative terms like "frustrating contact", manipulating the order etc.
Also do you have any evidence? Saying what she's doing isn't enough - that could just be seen as mudslinging - that is the danger. I did hint at PA once but had a social services closure report which backed it up.
Anyway your initial question was about your upcoming Cafcass interview. Any mention of alienating behaviours is really for paperwork and hearings later.
For the Cafcass interview you want to sound child focused and positive about co parenting. And make that the key.
Otherwise it comes out like - "She's doing xyz" which Cafcass will see as negativity about the Mother. I think what you want is a good Cafcass later and save the arguments about alienating behaviours for hearings.
Dads sometimes have a temptation to want to deal with the whole case with Cafcass and throw everything in - but some things are better addressed at hearings.
So you need to be careful what you say to Cafcass. All they are looking for, in this interview, is - are both parents safe. They will already decide that the Mother is safe because the kids live with her and social services haven't taken them away. So really they are looking at - are you safe.
Hence keeping it about the kids, and not about the ex.
IF Cafcass ask if you have any concerns, you can say, well it worries me that they parrot a lot of negative things from their Mother and say such negative things.
When you say you've had a lot of harrassment and abuse from the ex - in what way? In emails or messages? On the doorstep? Is there any evidence of this?
You want to keep it really calm and low key and say things like - it has been very difficult co parenting as you've been on the receiving end of a lot of hostility, verbally and in writing.
What Cafcass will want to know is WHY she is being like this now - so - has there been a trigger? New partner? A disagreement about something? You need to be able to say - no these things she is saying aren't true - I think she is just angry that I have a new partner/have applied to court.
That kind of thing.
Solicitors do tend to say - if you don't say something now you can't raise it later - they are probably just covering themselves. But it doesn't mean you have to make allegations! What you have to remember is Cafcass aren't Judges. I'm not sure I entirely agree with that advice anyway.
It's more like - if you don't raise something in your initial application, it would be harder to raise it later.
Cafcass are just looking for welfare concerns - to see if there are any. For the children.
Their common fallback is to say there is "conflict between parents" if both parents are accusing each other of things. Also if both parents accuse things, it could lead to a fact find and drag on - which means solicitors earn more money.
Sorry to sound cynical, but our advice for a Cafcass call is - don't say anything negative about the Mother. Or Cafcass will side with her!
The call needs to be about the kids - not the ex. However, it depends what Cafcass ask you. Sometimes they just tend to chat generally and then throw a fastball like "Mrs Ex says you have done xyz". The main thing is not to react and not to retaliate. You can pause - but a good answer might be "I'm sorry she's saying these things because it's not true. She does seem very angry towards me generally and it has been very difficult". Then you change the subject.
Move onto how great the kids are - what they like doing with you. Speak genuinely about the kids and your care for them will shine through. That is what impresses Cafcass - sounding like you care about the kids rather than attacking their Mother.
So two mantras: "Don't say anything negative about the ex" and "I just want our children to have happy loving relationships with both parents".
Cafcass should have ALREADY seen your application. So - did you raise the things the ex was doing in your application? If so you DON'T need to raise them again.