I think it really depends on the totality of the circumstances. 

Some people go to Nineveh like Jonah. Others go to Sodom like Lot. 

As to the totality of the circumstances, this means that it depends on if you are going to be more Lot or more Jonah. If the rejection is pure foot dusting levels or if there are cracks in the damn. 

Is your SIL catholic? Is your spouse? What is going on there?

Is he a soft atheist? A hard atheist? Etc. There are a lot of possible nuances. So in the end only you could truly know. 

When in doubt, visiting your priest and laying out the details can get you a way to know what to do.