This kind of situation with conflicting loyalties and needs can tear a family apart. I’m glad you wrote to us.
From where I sit, your stepson has multiple problems. He is marrying so quickly after a divorce that he isn’t giving himself time to learn from the experience of a failed marriage. He doesn’t seem to understand that whatever his feelings for his former wife, she is still the mother of his children, your grandchildren, and is deserving of some respect, if only for that. He seems to be asking you and your husband to take sides in a no-win contest of love and loyalties. He doesn’t seem to be considering how his kids will feel about meeting this woman who has taken their mother’s place in his life and his bed.
Meanwhile, your husband is torn. He doesn’t want to lose his son over all this but he has made a commitment to the mother of his grandchildren and to you. He may have the idea that blood relationship comes first. But he isn’t considering that his grandchildren are also of his blood and deserve his consideration – even over his son. They are the most vulnerable people in this situation.
For the kids’ sake, my opinion is that if your stepson wants to integrate his new wife into the family, he needs to take it much more slowly. It’s unfair to displace his children’s mother from her home. It would be hard on the kids to have to have his new wife, their new stepmother, move right into their mom’s place.
One option would be for your stepson and his new wife to stay in a hotel or with a friend and to arrange daily visits with you and his children. If he really can’t afford a hotel room for a few nights, perhaps your husband could help him by financing part of it. This would not only solve the sleeping arrangements but would let your husband demonstrate to his son that he isn’t taking sides. Your daughter-in-law could cooperate by agreeing to go out while he visits with you and the kids. Alternatively, he could arrange to take the children out to some local attraction or event to give the kids a way to get to know their new stepmom without intruding on his former wife’s life.
Although I can certainly understand the intense feelings that go with this situation, I hope you and your husband will take a step back and rethink your positions. To me, the focus shouldn’t be on who has the “right” to be in your home (stepson or daughter-in-law). The conversation should instead be about how to support your granddaughters and how to integrate this new reality into everyone’s lives. Your stepson will leave after a few days. You, your husband, your daughter-in-law and the grandchildren will be left to deal with the emotional consequences of his visit. You want to make sure that whatever happens leaves everyone able to comfortably live together.
I wish you well.