Aw I still have lovely memories of my little girl looking beautiful as an angel with tinsel around her long blond hair in the nativity play at school. Don't worry about your daughter, she'll have a great time. It's just fun to them at that age, play-acting. My daughter is an atheist now, even though she was Mary in one nativity play at school. We have to let them join in to feel a normal part of human society but if you don't take them to church or continue talking about religion it all just fades away as part of their childhood. Just as its part of humanity's childhood.
The negative feelings you have from joining in with the holidays will fade. It's just the cult programming being triggered. Remember the brain is programmed by learning that some things are good and other things are dangerous. Depending on who tells us about the nature of the danger of course! It's an evolutionary survival mechanism. If you don't keep reinforcing the programming it does fade gradually and your authentic self will take over as you make positive decisions to do things you truly want to do. Have fun!