Just returned from a week at Casa Buendia and it lived up to its promises of providing luxury, family-friendly accommodations in an undeveloped part of Costa Rica. We visited with six adults and three toddlers (3 years old) and everyone loved it. There was plenty of room in the house and the kids loved the pool. Also, Erick and Yelba were fantastic, giving us tours of the property and helping out with little questions.
The house is also well-located. After a five minute drive down the mountain (4x4 a must!), you're minutes from Playa Hermosa (wonderful swimming beach) and Playa Dominical (fascinating surfer town). Drive a little further south and you're in Uvita - great grocery store, health clinic, and home to beautiful national park with stunning beaches. We never lacked for things to do.
Quick tips - while the water in the home isn't potable, we had no trouble getting water from the local groceries and no one in our party ever got sick. Erick and Yelba were also able to provide air mattresses for the kids so they could sleep in the rooms with the parents - worked great. Finally, the house was an easy 3 hour drive from San Jose; however, on our trip there, the Caldera Highway was closed unexpectedly and it took about 4 hours and 30 minutes to get there (but we had a surprise tour of rural Costa Rica!).