Interesting times coming up - we are to visit my in-laws again for a week.
I have had no contact with them after we came home from the last visit (when they told me I'm a narcissist and a sadist and trying to get into their money) but that's is no different from normal. I still feel quite hurt by the things they said, and I'm a bit worried I might slip from my planned approach of "distant but cordial" into "hurt and passive-aggressive" if I am not careful. :/
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Well, I would take some time to think through how you'll react in different situations.
What happens if it blows up again, despite your best efforts to remain tolerant? Your wife - for whatever reason - decides to go that route again and triangulate a conflict between you and her parents. Maybe she greatly exaggerates something you said or did that she didn't like, or maybe she makes something up out of whole cloth?
What if there's no blow up, but a bunch of snide remarks, or references to last time?
What if it goes really well, or they even apologize for things said?
I think if you're mentally prepared for these things, you're less likely to slip into passive aggressive mode.