The important question here is what does your lawyer say, and why are you asking here? Custody and visitation cases tend to go very badly without counsel, so do what should have already happened - get a lawyer. Note that custody itself can still change in the case, so you have a lot more than your narrow question at stake.
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You are certainly entitled to enjoy holidays with your children if you celebrate them. The real question is did you have these same beliefs prior to the marriage? If she new you didn't really celebrate holidays yet she chose to procreate with you then I think you should still be able to have your kids. regardless of whether or not you celebrate the holiday.
I believe it is unreasonable for her to demand 100% of the holidays, particularly if you two live in the same general area and she will have "regular" visitation. Sometimes when the parties reside far from each other and the non-custodial parent cannot reasonably exercise "regular" visitation the court may try and make up for that by awarding more holiday and/or summertime visitation. But even if that is the case, 100% of the holidays are unlikely. If you do not have an attorney, you really should have one. This case is about more than money (most cases with a few exceptions are purely about money when everything is whittled away), this case is about your child and your relationship with the child. Things can go very badly in these cases when unrepresented.
It is unlikely in my opinion that the soon to be ex will get 100% of the holidays. Holidays are not just about celebrating. It is a time for children to spend meaningful time with parents AND extended family. First- you should not be representing yourself in such a delicate situation. Second, we cannot tell you how to practice law. However, if you were represented by an attorney, that attorney would call your extended out of state family as witnesses to inform the judge how important you and the children are to the family. I suggest looking at the factors contained in O.C.G.A. 19-9-3 (custody statute). You should also prepare your parenting plan in great detail. You can find sample parenting plans on the Cobb County web. Again, I HIGHLY caution you against appearing in court without counsel. These are your kids. You could lose every holiday because you are not trained as an attorney.