We've visited Hacienda Panilla (Marriott) several times on our many trips to Costa. It's a fairly short ride from where we stay. A bit too pricey for us but it's always fun to check it out and pool crash the place. We've been staying at The Sanctuary at Playa Azul for years now(since 2003). It's an amazing 80 acre condo complex basically in the middle of the jungle. We like it because it's completely removed from the hustle and bustle of the major tourist towns of Tamarindo and Nosara. Granted it's a bit of a drive to those towns but there is a good challenging beach break like 10 mins away. I can put you in touch w/a couple of the owners. We rent directly from owners as it's always much less than booking through the resort. We first found an owner on VRBO but I don't think they list there any more.
Good luck on your quest to find the perfect anniversary stay in Costa Rica.
http://www.sanctuarycondominiums.com/

Hacienda Panilla


Our home away from home at The Sanctuary


Condo at The Sanctuary at Playa Azul


One of the two pools at The Sanctuary


The break near The Sanctuary