The one thing that was the hardest for me to learn, was to respect the choices my children make. I think you will have to let go of your judgment of your son-in-law. Even if you don't say anything, they will sense it if you do not release it.
If I were you I would have a good, hard look at myself and try to get to the bottom of why you really feel the way you do. If you could come to terms with it and make a heartfelt apology to your SIL and daughter, you have a chance to share in their lives. If you don't you will be pushed aside. Imagine if you were in your daughter's shoes and your mother treated your choices so disrespectfully? How would you have felt?