I like them, as a group.
Iivo looks foreign (also kind of spicy? maybe because it's almost an anagram of olive) to me, and I don't have much if an opinion on it.
Yvo reminds me of
Yves, which I like a lot, and
Yvo seems more relatable to me than
Yves does.
Ivo kind of looks like a cross between
Yves and
Ivan to me. It's okay, but if you don't want it pronounced eye-voh, I'd probably go with a different spelling.