Despite all of this, one of my biggest fears is that my wife and parents won't get along.

Don't be too put off by comments. This is very much a possibility - the people with good relationships with their inlaws aren't the ones who are going to be making posts so you won't see them. They exist - my own mum and grandmother get along so well and my grandmother pops into our house when she wants to and they speak most days etc. So do my mum and my SIL. May Allah preserve their relationships. I can think of other examples too. It takes time and very often, it can depend on personalities aswell. I wouldn't stress too much - just keeping making du'aa and may Allah accept.