You won't be able to maintain the same relationship with in-laws. As pp have said, blood is thicker than water, and the blood between in-laws and their children is thicker than that between in-laws and their grandchildren.
I left exH because he was abusive, ex-MIL has not only stopped contact with me, but also with her only grandchildren (exH is only child) - has not seen them in nearly 2 years now despite living in same city. The one time I spoke to her since, she told me that it is all my fault because I was not a good wife to him. Ex-FIL still sees me and his grandchildren as exH only allowed supervised contact with DCs, and so ex-FIL provides the supervision. I still don't think ex-ILs actually believe that exH was abusive but that somehow I invented all of it (despite court documents, medical evidence, police evidence, etc.). Ex-FIL even told me recently that the situation is harder for exH than it is for me.
Your in-laws will really not care about you, their DS will be their top priority, and they will believe whatever he tells them.
Agree with others that let them do the driving if they want to see their grandchildren (grandparents don't automatically have any rights in case of divorce/separation, it's up to the kindness of your heart and wanting to do what is best for your DCs). Take care of yourself, you're the one who is pregnant and has kids to look after.