Respect the bond and privacy of your children (daughter and SIL). Even in your home, they are entitled to interact with each other without your involvement. Hopefully they will want to do that. Recognize it, take note of it, and give HKB”H gratitude that they love each other.
This young couple is their own family, and you are only extended family. Let them spend Shabbos and YomTov wherever they wish, whether at the other sides home or at their own home. Invitation should open, but never, ever imposing your own needs on them.