She shouldn't come especially since it's a family event. Your mother isn't bringing her current bf. cousins or other non-immediate family who want to bring a plus-one are different (in anticipation you bring that up). That being said you already invited her. It's a little late now. Pressure or no pressure. She isn't family and he's only seen her approximately one year, so her children aren't invited. If she can't find a day sitter then she can't come. That'll be her problem to resolve. It's your day and you don't need half a dozen children of a gf who your father only knows twelve months coming to a family event that is he most important day of your life. If you absolutely must retract the invitation be firm and resolute about it, no wishy washy attitude. Make it clear you want only family there. Your mother isn't bringing anyone so he can't. Any cousins who might bring somehow are extended family and it won't be an uncomfortable situation. Her coming makes your wedding day uncomfortable. Therefore it can't happen. The focus is in the wedding not outside drama. He may decide not to come, that's a risk you take. There's no perfect solution. If I were you I'd allow her to come but without the kids, only because she's already been invited. However it's reasonable to disinvite since your mother isn't bringing anyone and this person isn't family. It's just bad form to disinvite a guest and won't make things comfortable later if you ever have her over for thanksgiving or any other family function. You'll have to decide which is more important. Being uncomfortable and did inviting using an excuse, or allowing her to come since you already invited her and saving the uncomfortableness that will come later when you ever have her over for a future family holiday.