It doesn't really matter what the others are going to be.
It more about establishing, with your DH that the two of you need to support each other in your choices, especially to others, including his parents, even if you don't always agree. This is especially important in those first few weeks.
And with PIL it's about establishing now and carrying on being firm about boundaries. If I were you I'd be talking to PIL now about some of the cultural differences you see. To try to open them up a little to the idea of there being different ways of doing things. I read French Children Don't Throw Food which helps me understand what their expectations are (although that book glosses over how that achieved, the shouting, physical punishment and control, control, control that is present in a lot of French parenting). I wish I could give my PIL my favourite parenting book to read but it is not available in French and their English is not good enough to read it In English.
My French isn't great either so the language barrier is a factor. This cuts both ways: I can ignore things I don't want to agree to, and the detail of their strongest criticism passes me by. But also, I'm not able to explain to them why I'm doing what I'm doing. So they (full believers in control and micro management) think I'm lazy and irresponsible when really I'm giving DD the Space to work it out for herself. But there again, if I was fluent, and I could explain what I really think we might have such a clash we'd never recover from it. At the moment DD has strong opinions (being three) and they hate that I respect and defend her choices (what the wear, games to play) rather than force her to do what they want. I spent a lot of our last visit saying 'I'm sorry, she doesn't want to' or 'she's chosen this one'.
So get ready to set your boundaries, to say no. To be firm, to be disliked, to be strong in the face of pressure and disapproval. At the start you can say 'I'm not ready for that yet'. And the over time make clear not yet means never.
What are they like in general? Do they back off if you say no thank you? Especially in the first few weeks I'd consider getting someone from the uk to come and stay to provide a counter balance. Has to be someone you love and trust though.
Know this is something that could take several years to establish. And may not be good. I'm now accepting that PIL will always think they could do it better and think I should just hand her over! The upshot is a) I don't trust them b) (now) DH is frustrated too as he's got his confidence and knows DD is thriving, so he draws the boundaries and tells them to back off. C) at the moment DD doesn't like them that much because they treat her as a doll, wanting to impose their will on every detail, never listening to to respecting her wishes.
We're in a run of spending more time with them than usual. I am trying to manage the next couple of visits better by emailing in advance to manage expectations. So what's her routine, ideas of things shed enjoy doing with them, what they should stay out of etc. Last time I left this to DH but he doesn't offer up much detail and MIL loves detail. I also I try to find small things where it does work to leave them to it to do it their way, and then back off at those points.
We hoped they'd get to know us and DD better with more contact. But overall It's not working, and PIL continue to make it clear they think I'm doing most things wrong (although DD is thriving) so from now on we'll keep contact to fewer shorter trips.
Having said all that, you may come to an understanding and be grateful for their support. For me, the crucial factor is whether they are respectful and accepting of your and DHs choices even if they'd do it differently. My PIL are not and I now realise never will be, but yours might be different.