I tried searching for unisex baby clothing to see how they are buttoned, but couldn't find much. Most of it is gender specific. Are you planning on selling these items or is it for a gift for someone you know? If it's a gift I'd suggest waiting or use a gender neutral color OR if you know how the parents feel about color you could go with that.
As for buttoning..as Ingrid says I wouldn't worry too much about it. You could also skip the buttons entirely and put a tie or two on it near the top.