I left DP over his lack of relationship with our DC (as well as his infidelity) and have been trying to facilitate contact since but it's so difficult. We have a new born son as well as the older DC, plus ex DP is sofa surfing, so contact has been at my house or with me there. He won't take the older ones alone, they would be distraught if he tried and TBH I don't trust that he could keep them safe because they actively run away from him.
Yesterday he came on an afternoon to the park with us. All DC refused to sit on the same side of the picnic bench as him. None of them would have him push them on swings- they'd rather not go on them than have him near them. Every time he talks to our 3 year old, he shouts 'I don't like you!' and runs away to me - resulting in him getting hit by a swing yesterday because he was so desperate to get away.
They are so much happier when he isn't around; it's like a weight off their shoulders. When he's there, they're over emotional, tantrumming and miserable. They cry at the prospect of seeing him, don't enjoy his company at all and spend the whole time utterly miserable. I don't know how to improve things but I don't want to keep seeing them unhappy and even hurt because of contact.