OK, here are a few suggestions, Jamie. First of all, most of the recommended places will be on the Pacific side, as the Caribbean side tends to be more...Caribbean in the vibe, more ganja-fueled, less Costa Rica.
Of all the places I talked to the guy about, Cabo Matapalo sounds like it'd be the coolest place for the wedding or at least the honeymoon. Not very touristy, on the edge of a rain forest preserve, lots of eco-lodges and stuff like that, beautiful beaches and such. Google turned up
http://www.junglehouse.com/ as one of the first results, to give you an example.
Dominical is another really laid back and non-touristy kind of place, the naturalist paradise type thing.
Tamarindo, is pretty trendy, not quite as touristy as the main digs, not overrun by tourists but still kind of a hot spot.
Jaco, on the other hand, is very touristy, where you get all the casinos and stuff, so sometimes it's a question of guest consideration. I mean, do you want them to live it up in the tourist/casino hot spot or more of the naturalist area?
On the Caribbean side, you'd probably want to look at Puerto Viejo.
Hopefully this gives you a good starting point for googling and such.
