4 And he answered and said unto them, Have ye not read, that he which made them at the beginning made them male and female,
5 And said, For this cause shall a man leave father and mother, and shall cleave to his wife: and they twain shall be one flesh?
6 Wherefore they are no more twain, but one flesh. What therefore God hath joined together, let not man put asunder.
At some point its not about your parents, its about what you believe and care about. Although your belief systems will come in conflict on their own, I would not allow anyone’s parents to have a voice in your happiness. If they truly love and care for you, they should be happy for you, if your mate makes you happy.
If your hungry and they eat a meal it won't help you, you have to eat in order to get full. In that respect, your relationship is your food and your parents will not get full as you partake. The faster way to be unhappy is to try to please others.
I think the unequally yoke aspect of your conflicting faiths will require some negotiations that you should really take seriously or your holidays will be miserable… :o)