Unless my parents are Meryl Streep and Daniel Day Lewis, I'm pretty darn sure they adore my DH.
Similarly, I was pretty darn sure they had deep reservations about my Ex-H, but didn't say anything until things blew up, always supported and did all the family stuff and acted like they liked him but we both knew the truth. People can read.
Point being, your daughter knows. Your SIL knows. It's not about the money, but they have a marriage where they know that at least one set of parents is unhappy. Ouch. That's something that doesn't help any marriage.
IDK, I don't have kids, so it's meaningless, but I'd be more concerned with ensuring my DD had a happy successful family, then where the bits of paper and numbers ended up after I was dead.
OP cannot "ensure" that DD has a successful family. That is DD's & SIL's responsibility - not OP's. (He CAN avoid deliberately seeking to stir up trouble.) Many couples have money issues, they have to work it out, not depend on the money of a parent. (Gifts here and there are fine.)
As to the bits of papers and numbers, is that referring to OP's
life savings? OP may view the years he put into accumulating the potential inheritance for his children as something less trivial than bits of papers and numbers. I know I do.
OP is young. His daughter could easily be pushing 60 by the time he passes. A secure inheritance could make a huge difference in her senior years. There are plenty of women who do have to start over in this 50's following a divorce and it's not necessarily easy.
And as to in-laws not liking the son or daughter in law. When we started out, it was not a question of "reading" the truth. It was in-laws screaming at the top of their lungs. A week after our wedding my MIL stood in the street screaming about what a horrible person I was. When I was accepted into graduate school, MIL told my DH to divorce me, take the children back to Europe and she would find him a new wife who wouldn't work outside the home. My parents were no bargain to begin with either. (We coordinated our own defense strategy. Neither were disrespectful to the in-laws: the blood child would go to the defense of the spouse.) Over time, my parents came to love DH (he deserved it), and my in-laws me.
We are now in-laws, and our goal is to treat the children and their spouses with respect and to not be overly intrusive. I/we haven't made up my mind as to how I/we leaving assets, but whatever I/we decide, they will just have to deal with it. All children are loved, but not all have equal needs.
But, bottom line, it's up to the spouses to grow-up work out their own marriage.