I just don't think they'd have kids. They have goals and that has been what they wanted for years and still want to get to the top. And also pay for what they did so they'd leave a kid behind. Saw what that did to Ed and Al.
See I just don’t see the war crimes trial happening. I think they are open to that, would accept that, but the reality of it is it’s just going to dredge up so much that will actually be counter productive to what they want to achieve. And seeing Amestris through to a democracy is no overnight task.
But I agree they would fear leaving a kid behind. They did see how desperate the Elrics were and they experienced the loses themselves. They see Elicia growing up without a Dad, Winry without her parents. Its hard to not fear it and its last thing they would ever want to happen.
I also think they are more aware of their mortality and age now. Its canon they are both age sensitive, but now they are both in their 30s and have some severe past injuries that plague them. Roy has a scar on his side, two hands that were skewered. Those hands ache in bad weather and probably have reduced function. He’s no longer the spry Colonel who leapt all over the place in an alchemy battle with a teenager. Riza had a life threatening slice to the neck, that left a scar and maybe decreased range of motion. They are feeling older, what plans they made in their 20s to change the world were done feeling like they had a lot of time. Now, time is ticking. Makes you think differently. Makes you ask, “Am I going to regret this later?” when you make huge decisions. And they have so many regrets already.
I see all the scenarios as plausible, I don’t disagree with any of them.