I like
Emerson better, and it seems a little less trendy to me than
Addison, but I love nn
Addy! I tend to like surnamey first names, esp. for boys. I also like that you've stuck with the traditional spelling, instead of Emersen or Adisyn etc.
Grace goes well with both, but maybe
Addison Grace and
Emerson Rose?
Also (if you're liking the more masculine fn with a traditional feminine mn, if not, this may not help at all):
Elliot Ruth (nn.
Ellie?)
Quinn EleanorBlair FelicityLane ElisabethKennedy Rose