How to deal with bullying from in-laws 😓

My in-laws are old school Africans who live by “you do whatever the elder says and you can’t question them”, we’re visiting my husband’s home country this summer, it’ll be mine & LO’s 1st time however I can only stay 1wk due to work commitments. I’ve shared this with both MIL & FIL as they were planning a party for me but they don’t seem to get it, they’ve made it clear that I should make my schedule work. I don’t how to when my line of work is driven by client requirements and when we first agreed the dates for the visit, I was on maternity leave so didn’t have visibility on what I’ll be going back to. They’re even going the extra length to invite my family despite knowing I can’t make the date. Unless I quit my job and become unemployed I don’t see how I can meet their expectations 😓 I see it as indirect bullying with the way they’re handling it and the things they’re saying especially when this is tied to my career something I’ve worked so hard to build, I’m now at a point I’ve disengaged from them both and not sure what’s the way to move on from here. P.S. they won’t listen to their son who’s numerous times told them I can’t make it and we should look for an alternative date