There are legal provisions in many or most states for parents who have schedules which cannot be determined far in advance, generally these are intended to protect flight crew, truckers, and similar. Your lawyer should know about this, at least whether it is an option in your state. Generally it's not going to be something you have to negotiate, the law will specify that's what she has to deal with. How often you get the kids on your days off is subject to debate.
I had a Navy buddy (UPS captain) who lived in a state which did not automatically apply that kind of protection. When he plead his case, and the judge told him sorry, he would have to get a different job if he wanted to see his kids. He said OK, he could get a corporate aviation job in the smallish town they lived in. Said he would submit his resignation that day, and be back in court with a copy later in the afternoon.
The ex, who obviously had her lifestyle planned out based on UPS CA alimony, jumped up in court and said Hold On! we need to talk about this offline!
She came to a reasonable agreement about shared custody very quickly, with the gravy train teetering off the rails...