Maui Wedding Wedding in Maui, Wedding Photographers

We're going to honeymoon in Hawaii from April 19th to May 4th, split evenly between Oahu (Honolulu), Maui, and the Big Island. Which island is the most expensive? Is it expensive just to eat out at moderate-level restaurants? What about take out places, and supermarkets? How about souvenirs and such?

I've done my research on activities, tours, luaus, golf and spa, and we've booked a few expensive dinners (it is our honeymoon after all) but would like to know how much the day to day would be.

Thanks!