Well, with 4 boys I am assuming you would like something strictly girl, not that could be used for either a girl or boy.
Riley Avery Gavin Cooper and...?
Emma Kathryn- Emma Kate
Courtney
Shannen
Sidney
Reese
I am really just guessing at what you might like. Everyone is different. I like your boys names! We wanted Cooper but changed at the last minute and I love Avery...who knows maybe we'll have a #3 boy- We have a Casey and a Brady...and no plans for numero 3 as of yet.
Good luck.
Baby names are like a hobby of mine-I am always interested in what people name their babies. Are there family names maybe you could use for a middle name?