*refering to Deariee's comment: I too feel like Ed and Winry will name their children after dead people they loved. Nina is a best match so I don't think it needs a change. Theo on the other hand... I'm not saying it's not a wonderful name (generally I amor the name Theo) but after seeing the boy's smile for the first time they would probably remember Maes Hughes (I mean- SERIOUSLY, who wouldn't? It gives the exact same energy. Besides they loved Maes and both miss him a lot) And will call him Mason (Mase for short) or simply Meas, like the original.
btw, I think that Theo is not a good match because Edward never knew that "Father" first tried to name Hohenhiem "Theophrastus Bombastus" so he couldn't name his son after that name.