My 3 yr old (when we split up) cried her heart out when the ex tried to take her, so he didn't or I persuaded him not to take her, Knowing it was on our agreed schedule, but trusting I was not encouraging it and would work on it, he accepted it.
I put effort into persuading my 3 yr old to 'want' to spend time with her dad, saying positive things, which I could because he was OK with the kids. But I also told her (and my son) that I would come and get her later if she wanted me to. My ex wasn't happy that she seemed to not want to be with him, but he went along with it.
Each day it was my ex's time with my 3 yr old, I gave her choice, so control was handed to her. In no time, she was freely going with her dad - knowing she wasn't being forced and knowing that actually it'd be fun.
I hate not being with my kids. I feel lost! Also, it's a real pain distributing uniforms, clothes, pack lunch items, etc.
Also I have no family and I hardly know anyone here, so for many months when we first separated I didn't know what to do with myself when my kids were with their dad. I could have used the fact my daughter cried and encouraged it so I could keep her with me. But I didn't, because no matter how much I can't stand the ex (he was abusive physically and emotionally), I know she benefits from having her dad, and lately she's started to feel closer to him. My son has always been very close to him and wishes there were 8 days a week, so we had him 4 each.
My DD loves having her new sister - both kids love her to bits, but they are OK with the idea they don't see her all the time. But they do see her everyday for a short time because of the way I put the schedule together. My ex has the kids sleep over on nights that I've had them in the afternoon, after school, or all day on Sat. Maybe you can work something out so your 3 yr old sees her brother every day or does your ex live too far away?
I understand how hard sharing kids is,it's awful and I hope I don't end up sharing my third child in the future. I just hate it! But, unfortunately, just have to accept it, for the sake of the kids.
So in terms of CAFCASS, I'd propose something reasonable such that the siblings still see each other as much as possible.
I know CAFCASS don't prevent access if an ex smokes or drinks - my partner's ex does that, smokes in the house, and has kids with asthma, and it wasn't even questioned. They also don't prevent access based on your ex having relationships. Generally, if your ex has space, is free from any trouble related to children, he will be granted contact.
It sounds like he's applied for a court order, which is why CAFCASS are involved. They are there to analyse and assess the situation in some detail and advise the judge as to what the order should contain. The judge often goes with the recommendation given by CAFCASS. So in effect they are mediators between the children involved in the court order and the courts, acting on behalf of the kids, and they normally have a background in social services.
So just keep focusing on what's best for your daughter. Offer to have a schedule, but put conditions in (I did). The further apart your's and your ex's wishes are, the more you are handing the decision to CAFCASS and the judge. My schedule means I and my new baby daughter see the my older kids everyday no matter what! and it couldn't be argued against because it was so fair.
But I was pretty much in the same position you're in at the start. My ex had the family home,as I left (I rented), he has a lot of friends in town, all his family living near, he'd left his job a year before we separated, so he called himself primary carer, even though my daughter went to nursery. But he had illnesses that sometimes made him unsafe to be around and he drank alcohol sometimes during the day. But given all that, the court was more than happy with our arrangements.