Beach Wedding: Advice Needed!

OK, so my husband and I are leaving in two days for a long weekend in the Caribbean to attend a friends wedding. We are very excited not only because of the destination (St. Martaan, where I have never been) but also because this is the first time since our daughter was born that we leave her at home (with grandma, who, as you know, came from Paris to spend part of the summer with us and babysit when needed). So it is both a social and a romantic gateway for us.

I have never been to a beach wedding before and I have no idea what people wear to this kind of occasions but the dress code on the invitation says "casual beach dressing", so I take it as a clue that high heels and taffeta gowns are not appropriate.
I am pretty much set on what I am going to wear since I had some time to think about it but I will show you what my options are and I would love to hear which one you prefer.
While looking for a dress to wear at the wedding I had two criterias in mind: no silk (because I am going to sweat in the Caribbean in July) and I wanted something inexpensive (under $100) and beach-y. Also, I wanted to avoid the bridesmaid look, so I excluded pretty much all the JCrew "parties and occasions" offerings.
Actually I thought that I had found my dress quite a while ago on ebay. I always thought that the Jcrew Lucca dress from Spring 10 would be the perfect dress to wear to a beach wedding (if you don't remember it, don't worry: pics will follow). It was a store-only dress and as much as I liked it I didn't want to pay $95 for it (it seemed really overpriced); but of course when I missed it on sale I regretted not buying it FP. I stalked ebay for almost a year for this dress, that came in light blue and pale pink, and when one finally popped up in my size this spring and for a decent price ($49) I jumped on it even if it wasn't my favorite blue colorway but the pink one. I already knew about the wedding (even if wasn't sure that we would go) and I thought that the pink colorway would actually be a better choice for a wedding (it's a little more elegant, while the light blue one was more casual). What I like about this dress is that is a simple strapless tubular dress, but the ruffles make it dressy (the fabric is a stretchy cotton). It looks better belted so if I decide to wear it I will probably need a sash:

I accessorized it with with the bubble necklace in soft violet (almost a perfect match):

The problem with this dress is that my husband didn't like it (he said that I look fat in it, boo), so I started to look for another option. Also, I think it would be perfect for the ceremony part but a little bit under-dressed for the reception. I was considering a few Lily Pulitzer dresses but between the price, the prints that I wasn't in love with and the fact that they didn't look really "me" I never pulled the trigger on any of them.
So when I went to Italy one of my "shopping goals" was to find another dress to wear at the wedding.
I found two actually. The first one is a strapless maxi-dress in a beautiful turquoise color with a "Roberto Cavalli" type of print. It's a no-brand dress (I bought it in a little boutique) but it is really a showstopper and even if it isn't the kind of dress that I would normally wear I thought it was worth to buy it just for the wedding (it was also quite inexpensive):

I have tried to accessorize it with my H&M knockoff of the turquoise bubble necklace but it is too long, I think, and fights with the print on the bodice so I think that I will wear it with a shorter one that was a Xmas present from my aunt:

The other dress that I bought it's a Zara dark navy empire waist short dress with a beautiful beading on the bodice. I bought it not exclusively for the wedding but to have something dressy to bring on vacation with me. It has a overlay of faux-chiffon that makes it flowy and beachy:

The problem with this dress is that it could be a little bit hot because of the lining. Also, is more of an evening dress and the wedding is at 5 (I don't think that we will get a chance to go back into our room and change for dinner, otherwise I would probably wear the first one for the ceremony and this one for the reception). I could also wear it at the reharsal dinner the day before.

The last option is a Calypso St. Barth silk plisse dress with "rope" gold neckline. I am going to take it with me but most likely I won't wear it at the wedding because it's black and I don't think that anyone will show up in black at a beach wedding (if you had another experience please speak up):

That's it. As far as shoes option I am going to take my Espadrilles to wear with the short dresses (seen with the third dress) and a pair of flat golden thongs (the congetti ones from last year). I am pretty much set on wearing the second dress (the turquoise maxi), that can easily go from the beach to the reception to the dance floor, but let me know what you think and if you have another preference or know something that I should know when attending a beach wedding.

Thanks for your time, I appreciate your comments!