I think I've seen some shows or movies that have had Vih-Vee, but the correct way to say Vivi is Vee-Vee, because that's how it is pronounced in Kingdom Hearts II. Since that's the way its pronounced in one of Square Enix's games, that's clearly the way the right way which they had intended.

And as for Quina, I call him/her Queen-a; though I guess its dependent on how you pronounce things. Most Americans I've seen like pronouncing long vowel sounds and would also say Queen-a.