I voted for a gift certificate to the spa at the resort. I'm getting my BMs one and they told me how excited they are about it. Some other ideas...I got my BMs: personalized tote bags (ebay seller Linen Classics), pink/green jewelry pouches (I think these are your colors too and they're very inexpensive...HansonEllis Unique Wedding Favors - Wedding Party Favors - Bridal Shower Favors), cute beach-themed photo albums (Kohls), starfish necklaces (Kohls), luggage tags (Target).
I think they will love any of the things you've chosen, they are all wonderful gifts!