I love your son’s name.
I personally would aim for each of my kids to have a different first initial, and nothing matchy.
[name_m]Harlan[/name_m] sounds very similar to [name_u]Arlo[/name_u], and both have consecutive ARL. I wouldn’t do it. Too similar for my taste.
Also consider whether or not you want your daughters’ names to sound unisex/tomboyish or masculine.
I go by the boy’s name as a guidline. I consider it to sound all boy, but this site is acting like it is Unisex because of the orange color. Similar to [name_u]Marlow[/name_u] I guess.
Anyways, my point is that I would not want my daughters to have more masculine names than my son, because that could be awkward for him and your daughters, but specifically for your son. That is just my opinion.
Some people like alliteration, I am not one of them, but if you like it, then give your kids all A first names. If you go that route, I advise you try to find A names that sounds quite different on the first syllable and number of syllables each name has.
Example:
[name_u]Arlo[/name_u], [name_f]Asia[/name_f], & [name_f]Alice[/name_f] are great b/c each has a different vowel sound although they are all starting with A. You can still have the look of alliteration without the matchy theme.
Personally, I’d avoid anything in between. What I mean is, either they all have A names or they all have different first initials. If two have A names and one is left out, it may be unsettling to one of the children later.
I am not a fan of the names you have listed, besides [name_u]Arlo[/name_u], but, I am picky and have taste that is all over the name map.
If you like [name_u]Indigo[/name_u], [name_m]Harlan[/name_m], [name_f]Azure[/name_f], [name_u]Lake[/name_u], [name_u]Scout[/name_u], and [name_m]Joplin[/name_m]:
You may like:
[name_f]Amity[/name_f], [name_f]Astrid[/name_f], Adelai, [name_u]Adria[/name_u], [name_f]Asha[/name_f], [name_f]Avia[/name_f], [name_f]Avalon[/name_f], [name_m]Adriel[/name_m]
[name_f]Briar[/name_f], [name_f]Blythe[/name_f], [name_u]Brighton[/name_u], [name_f]Britta[/name_f], [name_f]Bryony[/name_f] or [name_f]Briony[/name_f], [name_u]Bryn/name_u
[name_f]Cyra[/name_f], [name_f]Cassia[/name_f], [name_u]Damaris[/name_u], [name_f]Dalia[/name_f], [name_f]Delia[/name_f], [name_f]Delphine[/name_f]
[name_u]Chandler[/name_u], [name_u]Channing[/name_u], [name_m]Chance[/name_m], [name_m]Chace[/name_m]/[name_u]Chase[/name_u], [name_u]Blake[/name_u], [name_m]Brooks[/name_m]
[name_u]Ellis[/name_u], [name_u]Everly[/name_u], [name_u]Ever[/name_u], Emberley/[name_f]Emberly[/name_f], [name_f]Eliette[/name_f], [name_u]Evan[/name_u], [name_u]Elias[/name_u], [name_f]Eira[/name_f]/[name_u]Ira[/name_u]
[name_f]Felicity[/name_f], [name_f]Fern[/name_f], [name_f]Freya[/name_f], [name_u]Finlay[/name_u], [name_u]Flynn[/name_u], [name_u]Finn[/name_u], [name_f]Fauna[/name_f], [name_f]Fawn[/name_f], [name_f]Farah[/name_f]
[name_f]Gaia[/name_f], [name_f]Gwen[/name_f], [name_f]Gwenyth[/name_f] or [name_f]Gwyneth[/name_f], [name_f]Glenna[/name_f], [name_f]Glennis[/name_f], Glynna
[name_u]Hillary[/name_u], [name_f]Hazel[/name_f], [name_u]Haven[/name_u], [name_u]Hollis[/name_u], [name_u]Holland[/name_u], [name_f]Iris[/name_f], [name_u]Isa[/name_u], [name_f]India[/name_f], [name_f]Indira[/name_f], [name_f]India[/name_f], [name_u]Ivory[/name_u], [name_f]Ivy[/name_f], [name_f]Ivanna[/name_f]
Joliet, [name_f]Judith[/name_f] nickname [name_u]Jude[/name_u], [name_f]Jessamyn[/name_f]/[name_f]Jessamine[/name_f], [name_u]Juniper[/name_u], [name_f]Jacinthe[/name_f], [name_f]Jade[/name_f], [name_f]Jada[/name_f], [name_m]Jasper[/name_m]
[name_u]Kai[/name_u], [name_f]Kaia[/name_f]/[name_f]Caia[/name_f], [name_f]Clarity[/name_f], [name_f]Coralie[/name_f], [name_f]Cambria[/name_f], [name_u]Leighton[/name_u], [name_u]Larkin[/name_u], [name_u]Lennox[/name_u], [name_u]Luca[/name_u], [name_f]Libby[/name_f], Libba
Maebry, [name_u]Micah[/name_u], [name_f]Nica[/name_f], [name_f]Nova[/name_f], [name_u]Perrin[/name_u], [name_u]Peri[/name_u], [name_u]Penrose[/name_u], [name_u]Penny[/name_u], [name_f]Primrose[/name_f], [name_u]Quinn[/name_u], [name_u]Quincy[/name_u], [name_m]Quinlan[/name_m]
[name_u]Robin[/name_u], [name_u]Rowan[/name_u], [name_u]Raven[/name_u], [name_u]River[/name_u], [name_u]Raleigh[/name_u] (sounds like molly with an r) , [name_u]Rhys[/name_u]/[name_u]Reece[/name_u]
[name_u]Shaun[/name_u], [name_u]Sheridan[/name_u], [name_f]Sylvia[/name_f] / [name_m]Sylvan[/name_m] / [name_f]Sylvie[/name_f] / [name_f]Stella[/name_f] or [name_m]Stellan[/name_m], [name_u]Sky[/name_u], [name_u]Seth[/name_u]
Merit, [name_f]Verity[/name_f], [name_u]Laurence[/name_u], [name_f]Tamsin[/name_f], [name_f]Taryn[/name_f], [name_m]Terrence[/name_m] nn [name_f]Terri[/name_f], [name_f]Tanith[/name_f], [name_f]Therese[/name_f]
[name_f]Unity[/name_f], [name_u]Vesper[/name_u], [name_f]Willa[/name_f], [name_m]Wesley[/name_m], [name_m]Weston[/name_m], [name_u]Waverly[/name_u], [name_u]Wynn[/name_u], [name_u]Wren[/name_u], Wrenna, [name_f]Yasmin[/name_f]
[name_f]Zinnia[/name_f], [name_f]Azalea[/name_f], [name_f]Noa/name_f, [name_f]Nola[/name_f]
[name_u]Sage[/name_u], [name_f]Reverie[/name_f], Claren, [name_m]Kimball[/name_m], [name_u]Campbell[/name_u], [name_u]Seren[/name_u], [name_u]Sequoia[/name_u], [name_f]Cerise[/name_f], [name_u]Cerulean[/name_u], [name_f]Whitley[/name_f]