They are both fun names. I agree they sound nice with your current girls. My association with
Despina is that very strong association with Cosi Fan Tutte... almost as strong as Cherubino. But not quite. I like her sassy character pretty well, and I love her aria.
I might chat with your music teacher if you're seriously considering using it! So she hears it from you first, and can share your amusement about it and feel sort-of honored.
I have a friend who really, really likes my middle name, which is a super random, rather obscure family surname. In high school she used to use it in her top combos for babies. I felt a bit affronted by it. I wouldn't feel affronted today, but I would think it was weird and totally random.
D is sort of an underplumbed letter.
Davina is another one in that group, maybe?
Diantha?