What would you do if your spouse doesn't agree on something because of his beliefs, and yet you think it might benefit your family?

If this is religion related, the best thing you can do is to try to meet each other in the middle. I'm of faith and my partner isn't. Alot of our important decisions, unfortunately, need to involve religion mainly because of my parents. For example, our nuptials have to be a religious ceremony as per my parents wishes. He is not necessarily too pleased about it but he agreed to it anyway, which I am thankful for. In return, I promise that the reception will be up to his wants and desires. Instead of ultimatums, perhaps you can try to meet in the middle, especially if it's for the benefit of your family.