We're getting married in Kenya next year and I have brought white linen suits for the males to wear but now I don't know what colour shirts and ties for them to wear???
Your wedding sounds like it will be a beautiful destination. The groomsmen should wear a shirt color that compliments your bridesmaid dresses. Since their suits are white I would make sure that the color shirt is light/pale. If you have dark or bright colors (for the girls) then just have the men wear a lighter shade. If you feel that the color is too girly for the groomsmen then they can always wear a neutral color like light tan or khaki.