Great list! Here are some combo ideas which I think compliment each other nicely:
Girl/Girl:
[name]Eleanor[/name] & [name]Beatrice[/name]
[name]Isobel[/name] & [name]Amelia[/name]
[name]Lyra[/name] & [name]Hazel[/name]
[name]Phoebe[/name] & [name]Isobel[/name]
[name]Hazel[/name] & [name]Carys[/name]
[name]Matilda[/name] & [name]Beatrice[/name]
[name]Matilda[/name] & [name]Hazel[/name]
[name]Matilda[/name] & [name]Eleanor[/name]
Have you considered: [name]Olive[/name], [name]Imogen[/name], [name]Annabel[/name], [name]Freya[/name], [name]Violet[/name], [name]Fiona[/name], [name]Charlotte[/name], [name]Celeste[/name], [name]Eliza[/name], [name]Clara[/name], [name]Cora[/name], [name]Flora[/name], [name]Daphne[/name], [name]Elodie[/name], [name]Theodora[/name], [name]Alice[/name], [name]Hermione[/name], [name]Penelope[/name], [name]Clementine[/name], [name]Lydia[/name], [name]Sylvia[/name], [name]Adelaide[/name], [name]Eloise[/name], [name]Isolde[/name], [name]Astrid[/name], [name]Cosima[/name], [name]Iris[/name], [name]Cecily[/name], [name]Tess[/name], [name]Josephine[/name], [name]Juniper[/name], [name]Primrose[/name], [name]India[/name], [name]Coraline[/name], [name]Jemima[/name]
I like [name]Willow[/name] too, but I’m not sure what it best goes with from your list.
Boy/Boy:
[name]Henry[/name] & [name]Oliver[/name]
[name]Lorcan[/name] & [name]Finbarr[/name]
[name]Cassius[/name] & [name]Orion[/name]
[name]Rowan[/name] & [name]Beckett[/name]
[name]Leo[/name] & [name]James[/name]
[name]Henry[/name] & [name]James[/name]
[name]Henry[/name] & [name]Leo[/name]
[name]Beckett[/name] & [name]Oliver[/name] (maybe)
Particularly with your boys’ list I think it’d pay to think about future sibsets (if you plan to have more kids), because [name]Lorcan[/name] & [name]Finbarr[/name] will demand different sibling names to [name]Cassius[/name] and [name]Orion[/name], whose siblings will be different to [name]Henry[/name] & [name]Oliver[/name]'s, etc.
Have you considered: [name]Theodore[/name], [name]Jasper[/name], [name]Sebastian[/name], [name]Fabian[/name], [name]Jude[/name], [name]Oscar[/name], [name]Felix[/name], [name]August[/name], [name]Atticus[/name], [name]Rufus[/name], [name]Ignatius[/name], [name]Elliot[/name], [name]Finn[/name], [name]Alistair[/name], [name]Louis[/name], [name]Lysander[/name], [name]Jack[/name], [name]Dashiell[/name], [name]Hugo[/name], [name]Milo[/name], [name]Cosmo[/name], [name]Archer[/name], [name]Ezra[/name], [name]Alexander[/name], [name]Caspian[/name], [name]Linus[/name], [name]Ambrose[/name], [name]Julian[/name], [name]Ellis[/name], [name]Leopold[/name], [name]Arthur[/name], [name]Abraham[/name], [name]Alec[/name], [name]Cormac[/name], [name]Conrad[/name], [name]Gideon[/name], [name]Lyle[/name], [name]Rafferty[/name], [name]Auden[/name]
Boy/Girl:
[name]Phoebe[/name] & [name]Orion[/name]
[name]Hazel[/name] & [name]Rowan[/name]
[name]Henry[/name] & [name]Beatrice[/name]
[name]Henry[/name] & [name]Matilda[/name]
[name]Lyra[/name] & [name]Leif[/name] (you might consider them too matchy)
[name]Beatrice[/name] & [name]Oliver[/name]
[name]Isobel[/name] & [name]Oliver[/name] (I’d rather [name]Isabel[/name] & [name]Oliver[/name])
[name]Leo[/name] & [name]Matilda[/name]
[name]Cassius[/name] & [name]Lyra[/name]
[name]Lyra[/name] & [name]Orion[/name]
[name]Eleanor[/name] & [name]James[/name]
[name]Eleanor[/name] & [name]Henry[/name]
Good luck!