That's an interesting one Hachiman. Obviously you know your in-laws and spouse better than we so how can we speculate on how your wearing a kilt or not affect them? If it were me I'd take the challenge on to re-educate the in-laws and ask your wife to support you on it. She vowed to!
Also have a think about why you wear a kilt, so that when you're asked you respond clearly and confidently. We all have our reasons of course but they probably are about the same: deepening family connection, cultural tradition and pride, and comfort. Any others folks?
Well how could they argue against that?
Erin