A7S ii (for free) vs A7 iii (purchased second hand) for printable photos

Long story fairly short, I asked my mate his thoughts on the a7iii. He said he had an old A7s ii that I could have for free. Super generous I know, and I've got a baby on the way and am not financially comfy. But I'd somewhat budgeted for a second hand A7 iii and I want it for stills, not Video (what he purchased it for)

I want this for photos of my wife and kid, and our future holidays. I only have a short window before child arrives, and I don't want to be upset when I can't print baby photos in future. That's worth more to me than the camera. I'd like the option to print fairly large, even 50-100cm^2 if possible.

Should I pass up on the A7s ii and instead pick up an A7 iii if my goal is to take stills. 12.2mp to 25.2 mp is a decent amount, even if it's more about the sensor. Sharpness is important to me.