TIFU by telling my wife to call her relatives wankers.

So this tifu happened a few weeks ago. Some context, my wife's great uncle and his son came from England to visit his sister ( wife's grandma) here in the US that he hasn't seen in 40 years.

So we were at the park for mother's day getting to know them and eating pizza and letting the kids play on the playground. Everything goes well. We leaving the park and as we're driving away I tell my wife to say " See ya later wankers!" to her grandma, uncle , great uncle and his son. Without hesitation she does it ( very proud husband moment). We laugh and drive off thinking they'll find it funny. We found out a week later from her uncle that my wife's great uncle and his son were very offended and it took and good amount of convincing from her uncle and grandma that she didn't mean it and was only joking. My wife told me thats the last time she listens to me.

TL;DR: Told my wife to call her English great uncle and son "wankers" as a joke, they did not take it as a joke.