In-laws dictating vacation clothing

DEAR MISS MANNERS: A few months ago, my husband and I, along with his parents, his sister and her husband, decided to go to a lake resort for a week this summer. Each couple paid for their accommodations separately.

My husband’s sister married into a very religious family with a strict "modesty" dress code for women. When we are with just her and her husband, I don’t have to comply with it (they’re more liberal). But if her in-laws are there, my in-laws ask that I do comply.

I have done so when we visit this family, when we attend events hosted by them, and when my own in-laws host events to which they are invited. The reasoning is that I need to do so because their children will be present, and I should set an example (even though everyone knows I’m not a part of this religion). I am fine with this; these are not my events, so I follow the rules or stay home.

However, several members of this family, who live near the resort, have now decided they would like to come, too. My MIL texted me, "Sorry! But you’ll have to dress modestly!" And then my SIL followed up with a link to where I could buy a modest "bathing dress" with sleeves, a long skirt and "swimming leggings."

For the record, their dress code is quite strict. Women cannot wear pants, only skirts and dresses. Tops must cover shoulders and elbows. Necklines must be at the clavicle. Skirts must extend past the knee.

I was looking forward to this vacation. I don’t want to buy a week’s worth of modest clothing. I don’t want to wear a bathing dress. I want to wear my chosen clothing. My planned wardrobe for this trip is far from risque (my own in-laws are going to be there, after all!). But my one-piece swimsuit, sundresses (even with a shawl) and jeans/shorts/hiking pants still violate all their requirements.

My husband says he’ll "back me up," but he’s not going to "start anything." So it’s up to me.

Am I being rude for not abiding by modesty requirements on a trip that I’m paying for, and using my vacation days for? Should I give my MIL and SIL fair warning that I’m not going to comply (so that this family can decide accordingly if they want to come)? Is it best to ask forgiveness rather than permission and wear the clothing I’d planned? Or must I cancel and stay home?

GENTLE READER: Surely, this family must visit establishments where people do not abide by their dress requirements.

Miss Manners suggests a compromise: "I am afraid that I won’t be able to purchase an entirely new wardrobe for this trip, but will do my best to comply with the dress standards when we are visiting their rooms or are invited out by them."

If the family insists that this is not sufficient, then they will have to make their own arrangements not to see you.