*venting* groom's parents want us to change dates?

My FH's family keep forgetting we have set a date. We haven't sent out STD's yet because there's still 18mo between now and the big day, but we have told all our family and friends multiple times. They asked AGAIN if we picked a date and we told them again.
This time, his mom pulled it up on her calendar and started getting mad because it's a Monday. We picked it because it will be our 8th anniversary (and it works out the venue we want is $800 cheaper on weekdays). We explained this to her, and they just said "...but it's a Monday. That's not being considerate of us and people with jobs." As if he and I don't also have full time jobs? We both work 5-6 days a week, we get it weekdays are when people work. But we picked this date because it's special to us and it's not like we cant take a couple days off work.

My family and our friends have all been great about it and excited. It's just his family that keeps asking about it, asking if we're considering other days, trying to guilt us into changing it to the previous Sunday so more of his relatives can come (even though they aren't invited?). Also his sister just got engaged as well and now they're saying we might have to change our plans for her sake..... We got engaged first. Not to be mean, but Her plans have no influence on us. She's nice, but we aren't close, so I'm not about to ask her about her plans and change my plans accordingly.

Idk. Just venting. Getting really tired of them trying to give us their 2 cents when we aren't asking for opinions, we are telling you what's happening.