I think the house will be fine if it's only for a weekend. After that, people will start to get sick of each other, no matter how well they get along.
Please, please, please let me give you some advice about beach weddings in Destin. It's of course up to you, but I would NOT go with a beach wedding company. Their prices are outrageous, their decor is cheesy, and they usually won't walk far down on the beach so that you're away from the crowds. I cringe every time I see a destination wedding done through one of those companies - the bride and the groom look very uncomfortable when they realize they have such a huge audience of complete strangers. Here's an example of two beach wedding set-ups in Fort Walton Beach. Notice how they're set up right next to each other - they were both for similar times through different beach wedding companies, and neither company was going to haul all their stuff waaaaay down on the beach away from the other wedding.
Speaking of the crowds, you'd be wise to plan your wedding during the off-season. Your guests will probably not want to walk far down on the beach just to get away from the crowds, but if you set your wedding up in a spot right off the boardwalk (as a beach wedding company would do), you're going to have to deal with screaming kids, radios blaring, fat people in their swimsuits lounging about, people standing around watching, etc. All of that is going to be in your wedding pictures, and nothing ruins a wedding picture like people in their swimsuits standing in the background. If you have your wedding during a popular time of year for tourists, the beaches will be crowded no matter WHAT time you do your wedding (unless you do it at sunrise), and it will be the opposite of romantic.
That's not to say that beach weddings can't work - I've been to some that are beautifully done and incredibly touching. I would advise you to find a minister or a wedding officiant, and then rent beach chairs through a rental company. I used RSVP Weddings in Destin for mine, and they were really good. They can also provide decorations (awnings, rose petals for the aisle, whatever) if you're worried about that. There are also some beautiful parks and gardens to have your wedding at in Destin if you decide that a beach wedding isn't for you.
Some other things to think about
-You'll want to plan your wedding for either early morning or just before sunset. Any time other than that will be too hot (unless you get married in late Fall or Winter) and the sun will be too harsh for the pictures to turn out well.
-Weather is unpredictable in Florida, so have a back-up plan. That could just mean getting married in the rental house, getting married underneath a gazebo somewhere, or even being able to postpone the wedding time a little bit to wait for the rain to subside.
-It's usually pretty windy on the beach, so if you want your guests to be able to hear what you're saying, you might want to wear mics or talk very loudly. Also, you'll want to choose a hairstyle that works well in the wind - nothing that you'll have to constantly be pushing out of your face or that will be blowing in your face when your photographer is trying to get great pictures.
-In regards to all the background noise at the beach, you might want to think about whether you really want to walk down the aisle to music or not. I've seen a few beach weddings where they tried to blare music over speakers when the bride walked down the aisle, and it simply does not go over well. The guests can't really hear it over the waves and the wind, and there's so much open space that it comes across sounding tinny.
-Don't wear heels! If you're doing a beach wedding, embrace it and go barefoot or wear flats. This seems like it should be common sense but MANY brides wear heels on the beach here, and they look ridiculous.
-Too much decoration on the beach just looks tacky and overdone. The essence of a beach wedding is in its simplicity. This is of course just my opinion, but I've talked to many brides who realized too late that the decorations didn't look right on the beach.
I hope this helps! Your wedding should be exactly what you want it to be, but I just wanted to give you some insight from someone who sees a beach wedding almost every weekend. There are definitely things that a lot of people don't think about.