My friend is expecting a baby through surrogacy. She and her husband are Jewish but the surrogate is not. I understand that there are some halachic questions with surrogacy. Is it ok to say mazal tov and give a gift when the baby is born?
Will this baby be non Jewish?
Correct. There are halachic questions about this, which are beyond the scope of a question to be answered on a website. Anyone who has such a serious question must speak with their Rov about it first.
Regarding your question, it is permitted to give a baby present and to wish the couple mazal tov.
Regarding if the child is considered Jewish or not, that is one of the questions the couple will discuss with the Rov that is advising them.