Beach Wedding Necessity?

So the future in-laws brought an idea to us last night. They heard from a friend of a friend about using paint brushes to brush sand from your feet after the beach ceremony. And while that's great, our wedding is in a month. We have plenty to do to get ready. And I've already spent a lot on little extra touches. And our wedding is at a Hilton with a beautiful, newly renovated pier, which has several foot washes, both stationary and with removable showerheads. So I'm not overly concerned. And I don't have time to DIY cute little paint brush buckets and signs, etc... I work two jobs, I go to the gym six days a week, and I have plenty left to do.



So is it wrong I tried to politely tell them it sounds like a great idea, but not for us? And then when they kept pushing, telling me I could do it for $40 or so, I pushed back harder. And still said no.
Had they brought this to me six months ago I'd have been more amenable.
Or if they wanted to do the work or buy them.
Am I being a brat here?