Sounds like a wise choice not to go to the renewal. And that is wonderful that you and hub are able to work those things out with each other!

Regarding your question, if there are times when you have to see your BIL or SIL, I recommend being pleasant. Pleasant doesn't have to equal "buddy buddy" but just a simple smile and hello....so glad the sun came out today etc. If you don't feel that you can be pleasant, aim for basic civility. A civil tone, formal remarks etc. If you find yourself becoming overwhelmed by resentment or frustration in a given situation, take a break....go to the bathroom....breathe...gather yourself. I have done that myself in uncomfortable situations. If that doesn't help, and you feel that your anger may spill out, just leave politely. It takes so much more energy to be angry and unkind to others than to simply be pleasant or civil. In the long-term, I think you'll feel better by choosing the peaceful path. Best wishes!