Yes, being in a warm humid climate has a huge impact on how long the food lasts. Scott has a good point about not leaving seeds etc in when trying to feed fresh. How have your birds reacted so far? You have the right idea focusing on veggies rather than fruit, but I find that when a bird is resisting fresh food adding a bit of fruit can help ease the transition.
I also have found that transitioning from dry seed to sprouts before switching to veggies seems to help for some reason - not sure why. I have yet to have any bird refuse sprouts, even my seed junkie rescue budgies who literally ate only dry millet before coming to live with me. Once sprouts are the main diet I have a lot better (or should I say quicker?) success getting them to try new things. Also, the smaller the pieces of food, the more likely mine have been to try it right away, when mixed with their sprouts. I always mix mine with sprouts, but many do not.