All of these names "fit" well with Carson and Dylan, style-wise. So if style consistency is one of your criteria, I think that any one of these names would work.
You asked whether Ethan is "too common now"; but there is no way to answer that because it all depends on how popular is "too popular" for you. I like variety in names, so I probably wouldn't choose a top-10 name, and perhaps not a top-100 name; but I would make an exception for a name that I truly loved and that seemed the best "fit" for my child.
Some names that I like with Carson and Dylan include: Gavin, Ryan, Brendan, and Sean. Among the names you listed, Zachary and Kyle are my favorites, followed closely by Ethan. I am not a fan of Logan; I just don't care for it.
All of these names "fit" well with Carson and Dylan, style-wise. So if style consistency is one of your criteria, I think that any one of these names would work.
You asked whether Ethan is "too common now"; but there is no way to answer that because it all depends on how popular is "too popular" for you. I like variety in names, so I probably wouldn't choose a top-10 name, and perhaps not a top-100 name; but I would make an exception for a name that I truly loved and that seemed the best "fit" for my child.
Some names that I like with Carson and Dylan include: Gavin, Ryan, Brendan, and Sean. Among the names you listed, Zachary and Kyle are my favorites, followed closely by Ethan. I am not a fan of Logan; I just don't care for it.