I say, and with God's help: congratulating non-Muslims on their religious occasions is permissible as long as it does not include words that imply agreement with their beliefs. It is preferable not to attend places where they display any of their rituals that contradict our religion. Al-Zarqa said in his fatwas, pages 355-356: 'In my opinion, a Muslim congratulating his Christian acquaintances on the birthday of Jesus Christ, peace be upon him, is a form of courtesy to them and kindness in their companionship. Islam does not prohibit such courtesy or kindness towards them... And whoever thinks that congratulating them on their birthday is forbidden because it relates to their belief in his divinity is mistaken; for there is no connection between this courtesy and the details of their belief in him and their exaggeration in it... If we understand the legal opinion on congratulation, we can determine the ruling on printing cards and trading them; for whatever is a means of what is permissible is permissible.' And God knows best.