I think [name_u]Hartley[/name_u] would go very well with your other girls!
Might I suggest that you consider a three syllable name this time around? [name_f]Miley[/name_f] and [name_u]Landry[/name_u] have two so it might be nice for [name_u]Emery[/name_u] and [name_u]Baby[/name_u] 4 to have 3 
I love [name_u]Avery[/name_u] from your list!
Good luck!
[name_u]Finley[/name_u] goes great with your set.
I like [name_f]Thessaly[/name_f] a lot.
As well as [name_f]Livy[/name_f], Verily, and [name_m]Henley[/name_m].
Seems like 3 siblings w/-y names would be a good reason to try something different, but [name_u]Avery[/name_u] isn’t bad. [name_u]Finley[/name_u] makes me think of The Addams family…it just sounds kind of creepy/silly…like Pugsly.
[name_u]Finley[/name_u] and [name_u]Avery[/name_u] are great choices! I also knew a girl in school named Stokely (pronounced Stoke-lee). I always thought it was cute and different. It seems to fit well with [name_f]Miley[/name_f], [name_u]Emery[/name_u], and [name_u]Landry[/name_u]. Good luck!
Thanks for the help! I think I’m really leaning towards [name_u]Finley[/name_u]. But, I really like [name_u]Hadley[/name_u] too.
From your list I prefer [name_u]Finley[/name_u] and [name_u]Avery[/name_u]. McKay is too surname-y and doesn’t end in a long e sound, while [name_m]Joley[/name_m] looks misspelled and is more feminine than your other girls’ names.
I think these names would also fit your theme (ending in y/long e sound, gender-neutral/surname-like, two-syllable, starting with different letters):
[name_u]Ainsley[/name_u]
[name_u]Hadley[/name_u]
[name_f]Ivy[/name_f]
[name_u]Rory[/name_u]
[name_u]Sydney[/name_u]
[name_u]Tierney[/name_u]
[name_f]Maya[/name_f]
[name_f]Briony[/name_f]
[name_u]Taylor[/name_u]
[name_f]Jaya[/name_f]
[name_f]Priya[/name_f]
[name_f]Tansy[/name_f] - Uncommon, nice meaning.
[name_f]Roxy[/name_f]
[name_u]Paisley[/name_u]
[name_u]Casey[/name_u] or [name_u]Cassidy[/name_u]
[name_u]Ruby[/name_u]
[name_f]Ivy[/name_f]
[name_m]Yancy[/name_m]
[name_f]Holly[/name_f] - I think it wears better than [name_u]Hadley[/name_u], and it’s less popular.
Betony
[name_f]Mallory[/name_f]
[name_f]Felicity[/name_f]
[name_f]Jessamy[/name_f]