Question: Is it permissible for a convert to attend his family’s Christmas celebrations?
Answer: Assalamu Alaykum Warahmatullah,
It would be permissible to attend such an event, since it would be from keeping ties with ones family. One can attend the social gatherings, but should discretely abstain from actively taking part in any “religious” activities.
[Ibn Abidin, Nashr al-Urf; Ibn Abidin, Radd al-Muhtar; Nahlawi, Durar al-Mubaha]
And Allah knows best