I am RC, DH is aethiest. DCs attend RC school. Loads of parents at school not married, makes no difference, if the children are baptised Catholic they are considered for a place- they are not judged on parents situation.
My DH is ok about RC education. He knows it is important to me as I am committed to my faith. We did make a deal that I would not force him to attend church events. He goes to school nativity because our kids are taking part- he is not interested in the christian story aspect of it. But a lot of non faith schools perform the nativity also so chances are he would be watching a nativity even if they had not gone to a faith school.
I attend all the school religious functions ie. school mass. DH is at work anyway so issue of him attending never came up. I take the children to mass on sundays- they actually like going as the church is very linked to the school and they see their friends there, they know the priest as he is often up at school and for them it is a very supportive and warm community. (For me also, one of the things I really enjoy about church- sense of community is brilliant)
The only time it was a problem for my DH was when my dd made her First Holy Communion. As you are RC OP you know that this is a special occasion in the church, my dd wanted DH to go but he was v. uncomfortable with it. He did go in the end because she asked him so nicely he could not say no. It was not through choice though and he was completely bemused during the service and did not really have a clue what was going on.
I guess you need to discuss this with your DH, could he tolerate attending certain services for the sake of the children? Would he be happy to just turn a blind eye to the children being taught something he does not believe in? Do you want the children to be educated in the faith enough to support them when he can't or won't? For me it was easy as a Catholic I could not contemplate my own children being a different religion to me. But you do not seem too fussed one way or the other so it may be a different decision.
BTW- my dc now in yr6, they have not been taught anything about sex education, contraception, creation , hell & damnation. But they have learned about love, respect, sharing, forgiveness (and evolution)