I've been reading this story over again tonight, and this really struck me. I don't know why I didn't notice it before. Maybe I was still to hung up on "time travel"! (That's a good thing, by the way. Like I've said before, I love time travel stories.)
Anyway
"I was just telling Clark that I figured you'd sleep in this morning. There's no little kids around to wake us all up. We'll save the early bird stuff for when the grandkids are big." She put an arm around Lois, handing her the cup of coffee. Lois rested her head on her mom's shoulder and closed her eyes.
This section is written from Clark's POV, so we don't really see Lois's thoughts on it. But I can't imagaine how much that sentence affected her.
We have Ellen talking causally, whom Lois has missed in her life for TWELVE YEARS! But Ellen is also causally talking about how they DON'T have young kids in the house.
This is a painful reminder for Lois that Christopher and Nate are NOT HERE. How much she was probably looking foward to spending Christmas with her sons as well as Clark.
At the same time, you can also hear how much Ellen is looking foward to having grandchildren in this reality. Which, in the reality that Christopher and Nate are in, she never got to see.
How painful/heartbreaking must that comment have been for Lois? And she had to pretend it was just the causal comment Ellen meant it to be. Lois's inner strength is really coming out right now.
