BTW, if one has such a problem, in terms of Gebrochts/non-gebrochts, perhaps that young COUPLE should invite those parents to THEIR home for Pesach. Problem solved. And it is only an issue if the HUSBAND’S parents only eat non-gebrochts, because a wife takes on her husband’s family minhagim.
My son-in-law only eats shmurah matzah the whole Pesach. We only eat it for the sedarim. When they come to us for yom tov, whether first or last days, I prepare all their meals with Shmurah farfel and matzah meal in those side dishs that I normally make with regular matzah. It is NOT a problem for my keilim, according to my Rov. We asked the shailah. I cannot believe that it would be different for gebrochts/non-gebrochts, but that’s why we have to ask Daas Torah our Shailahs.