Xmas eve, like T'giving & BF are days you can't really request off, but if your scheduler doesn't suck, they'll work around your schedule. Frex, we go to my husband's family on Xmas eve, so I'm available open until 4, and so far my ETL hasn't had issues with that. She goes around and asks people what their Xmas week availability is and tries to make it work.
If you're seasonal and don't care if you get kept on, go ahead and ask for it off or NCNS, but if you hope to be kept on, it helps to be flexible.