What about something unusual, but still decidedly feminine (maybe even a little frilly), but that has a more boyish/unisex nickname? Like:
[name_f]Alessandra[/name_f] “[name_u]Alex[/name_u]”
[name_f]Eleni[/name_f] (not sure how princessy it is, but there’s also [name_f]Madeleine[/name_f], [name_f]Gwendolen[/name_f], [name_f]Helena[/name_f], [name_f]Lenore[/name_f]/a, etc.) “[name_f]Leni[/name_f]”
[name_f]Charlotte[/name_f]/[name_f]Charlene[/name_f]/[name_f]Charlize[/name_f] “[name_u]Charlie[/name_u]”
[name_f]Arabella[/name_f] “[name_u]Ari[/name_u]”
[name_f]Isabelle[/name_f] “[name_u]Issy[/name_u]” (usually seen as a girls’ name, but I’ve heard guys named [name_m]Isaiah[/name_m], [name_m]Isaac[/name_m], and [name_m]Isadore[/name_m] referred to as [name_u]Izzy[/name_u], as well, so I think an [name_u]Issy[/name_u]/[name_u]Izzy[/name_u] name would work. I think [name_f]Isadora[/name_f] would also qualify here–I just don’t like it personally)
[name_f]Clementine[/name_f] “[name_u]Clem[/name_u]”
[name_f]Olive[/name_f] “[name_u]Ollie[/name_u]” (or even [name_f]Olivia[/name_f] “[name_u]Ollie[/name_u]”. I’m not sure how unusual I would go, though, since both of your boys have traditional, common classics; [name_m]Matthew[/name_m], [name_m]Benjamin[/name_m], and [name_f]Fairuza[/name_f], for example, seems very jarring for me)
[name_f]Samara[/name_f]/[name_f]Samira[/name_f] “[name_u]Sammy[/name_u]/[name_u]Sam[/name_u]”
[name_f]Theodora[/name_f]/[name_f]Dorothea[/name_f] “[name_u]Teddy[/name_u]/[name_u]Theo[/name_u]”
[name_f]Calliope[/name_f]/[name_f]Leona[/name_f]/[name_f]Leonie[/name_f]/etc. “[name_m]Leo[/name_m]” (I think [name_m]Matthew[/name_m], [name_m]Benjamin[/name_m], and [name_f]Leona[/name_f] would be adorable actually!)
[name_f]Catherine[/name_f] “[name_u]Kit[/name_u]” (or even an unusual [name_f]Catherine[/name_f] form, like Aikaterini or [name_f]Ekaterina[/name_f]…)
[name_f]Natalie[/name_f] “[name_u]Nat[/name_u]” (although my little sister is [name_f]Natalie[/name_f] nn [name_u]Tallie[/name_u], and I have to say, I think [name_u]Tallie[/name_u]/[name_u]Tally[/name_u] is the epitome of adorable! If I didn’t have a [name_u]Tallie[/name_u] in my life, I think I’d want it on my own list. :))
[name_f]Veronica[/name_f] “[name_u]Ronnie[/name_u]”
[name_f]Emilia[/name_f] “[name_m]Milo[/name_m]” (meh, a big stretch. But I think it’s sort of cool.)
[name_f]Jacqueline[/name_f] “[name_m]Jack[/name_m]”
[name_f]Wilhelmina[/name_f] “[name_m]Will[/name_m]”
[name_f]Georgia[/name_f]/[name_f]Georgiana[/name_f]/[name_f]Georgina[/name_f] “[name_u]Georgie[/name_u]”
I’m biased, of course, but I think [name_u]Ash[/name_u] is pretty edgy and cool for a girl. The options are pretty limited to [name_u]Ashley[/name_u], [name_f]Ashlyn[/name_f]/[name_u]Ashton[/name_u] (or the traditional Irish spelling, [name_f]Aisling[/name_f]/[name_f]Aislinn[/name_f]), and [name_f]Asha[/name_f]. Not very exciting, haha.
Or, you could go the other way around: a unisex name that comes with a girly nickname:
[name_u]Hadley[/name_u] “[name_f]Addy[/name_f]”
[name_u]Meredith[/name_u] “[name_f]Edie[/name_f]”
[name_f]Jocelyn[/name_f] “[name_u]Josie[/name_u]” (I [name_f]LOVE[/name_f] just [name_u]Joss[/name_u] for [name_f]Jocelyn[/name_f], but admittedly, it’s not terribly girly…)
[name_u]Harper[/name_u] “[name_u]Ari[/name_u]” (although [name_u]Ari[/name_u]'s unisex, so it’s not terribly girly, I suppose. I’ve always found [name_u]Ari[/name_u] to be pretty princessy, though, despite its masculine Hebrew origins, because of all the frilly [name_u]Ari[/name_u] names for girls–[name_f]Aurora[/name_f], [name_f]Aurelia[/name_f]/[name_f]Aurelie[/name_f], [name_f]Ariana[/name_f], [name_f]Arabella[/name_f], [name_f]Arianne[/name_f], etc.)
For some reason I really like [name_f]Penelope[/name_f] nn [name_f]Poppy[/name_f] for you, too–you get the floral with [name_f]Poppy[/name_f], it’s an unusual nn (even though [name_f]Penelope[/name_f]'s growing in popularity), and I find it really strong, thanks to [name_m]Odysseus[/name_m]'s wife in The Odyssey, but it also has a frilly sort of sound, which might appeal to your husband. It’s not rabidly popular, but familiar enough that I don’t think you’d have issues with. If you don’t like [name_f]Poppy[/name_f] for a nn, there’s also [name_u]Pen[/name_u]/[name_u]Penny[/name_u], [name_f]Nell[/name_f], [name_f]Lola[/name_f], [name_u]Pepper[/name_u], [name_u]Piper[/name_u], [name_f]Pippa[/name_f], even [name_f]Ella[/name_f]… I think it’s versatile and lovely, and I think [name_m]Matthew[/name_m], [name_m]Benjamin[/name_m], and [name_f]Penelope[/name_f] are lovely.
What are the names you have liked so far? And him? That might give us a better idea of what to suggest. (Also, your husband sounds adorable, haha. I can only hope that when I have a little girl in the future, and potential husband of mine would get so excited!)
Good luck!
ETA: Och, I just remembered that you’re [name_f]Katherine[/name_f]! So maybe [name_f]Catherine[/name_f] nn [name_u]Kit[/name_u] won’t work. Oops. 