My question is: If the non-Muslim is getting marriage and if both husband and wife are spending the night or enjoying the night, then is that they do Zina or is that Halaal?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

The majority of scholars are of the view that the marriage that takes place between non-Muslim males and females is correct and they confirm this fact. Some of them (scholars) deduced this from the saying of Allaah, about the wife of Abu Lahab (interpretation of meaning): {And his wife, too, who carries wood.}[111:4]. Their conclusion is that if the marriage had not been valid, Allaah wouldn't have called his wife. In addition, it is not reported that the Prophet or his rightly guided caliphs used to reject the marriage contract of the people who embraced Islam, but they confirmed the validity of their previous marriage and all rulings based on such contracts, like the rulings of family lineage and inheritance and so on. This of course is in the case where the woman is non-Muslim, as it appears from the question. But if the woman is a Muslim, then to know the ruling about this, please refer to Fatwa: 83425 and 81220.

Allaah knows best.