I like Kailani, though more so when I was younger. Now I do find it a little "cutesy", as you put it. You do have
Kai and
Lani to fall back on as nicknames -- somehow, they actually sound less cutesy.
I don't like Kaylani though; it looks odd and appears to change the pronunciation. The first syllable of Kailani rhymes with "sky", while Kaylani is like the name "
Kay". I don't think changing the i to a y is necessary at all.