I have no idea if he'd even turn up if I did tell him about it but if he does he might try and argue with me in front of DD and all the children there as I stopped DD's visits to him (on the advice of child protection, not because I'm a bitch or anything) and he is angry about that. He has form for getting out of control when he is angry (shouting, swearing etc.) and has done so at a daycare meeting before.
I don't think DD (5yrs old) will be fussed about him not being there, she is unhappy about him since the last time she saw him and refuses to speak to him on the phone except for a brief hello. He hasn't bothered to come here to see her since the last visit either even though he is allowed to.
But on the other hand he is her dad, and it does feel unreasonable to exclude him from big events like this, but he is very unwell mental health-wise and in denial about it so he doesn't stick to his treatment which means he is rather unpredictable.