Love Una /
Oona.
I agree that
Oona seems to carry around a bit more quirk, but in a delightful way.
Una, while having a charming personality, is more straightforward and respectable on paper.
I would consider both usable, and have met little Unas and Oonas in my life to cement that opinion.
I grew up with a name combination that carried the same sounds throughout, so it mirrors the "zany" quality of your choices with Homayouni.
I personally think that lighthearted feeling names (especially when you have a complicated or long last name) is a desirable thing. I really like
Una Homayouni, but I have to say that
Oona Homayouni is much more spirited to read! I quite like it.
Alliteration with
Henry Homayouni is fine. I have no problem with initial alliteration as long as it's not an unfortunate pairing (like PP). In this case
Henry Homayouni sounds like someone famous.