I would like to say that we worked it out together, but as he’s Incredibly lazy, I had to decide and tell him what was going to happen re access arrangements.
I based it on what was the most stable for my DD and most convenient for whoever was going to have to do all the school/nursery runs (me as it turns out). As she’s got older (7 now) I’ve let her have some input.
He collects her from school once a week, sometimes it’s an overnight sometimes not. Then we each have her EOW. In the holidays we’re more flexible but tend generally stick to the same days, e.g. she goes there overnight the same day he picks her up from school.
I wouldn’t make offers based on what’s fair for him, make it about what’s best for the children. This means looking at what the logistics are re school etc, what’s going to help them feel settled (bearing in mind the upheaval they’re having because of the separation). It’s their right to see their dad, not his right to see them.
Also make sure the arrangements don’t mean you facilitating contact - that was one thing I said at the start, stick to the schedule or don’t do it at all. No random swapping, swap things round only if absolutely needs be and with plenty of notice. That’s fair for the kids so they know what’s going to happen every week. There was a kid in my child’s class last year who was constantly upset because she didn’t know where she would be sleeping that night, because the parents never stuck to the elaborate and ridiculous access schedule they had agreed.