Hawai'i actually has a stop between the two i's, so you're all technically wrong
. Well, MMM had the best explantion :P .
/ka wa i i/ (IPA, spaces between syllables)
I'll try to approximate the sounds with the standard alphabet, but remember that I speak western American English.
kah-wah-ee-ee
For OP, just remember that vowels are kept pretty short (kinda clipped, really), so don't spend a lot of time on the 'ah' part of those sounds. Also, there should be no real emphasis on any one syllable--that'll come in by itself.