I have lived on island for 2yrs now.. really anytime is a good time to visit.. its more crowded in waikiki in the summer months.. but Aulani is FAR from Waikiki so unless you go into waikiki you wont have any problems.. winter months are more rainy for us but the showers are typically short bursts and then are gone.. you get bigger waves on north shore in the winter which is fun for everyone to go watch.. (notice i said WATCH.. not be in lol), and winter is whale season

... Temps stay around the same year round