My parents, brother, husband, 3 kids, and I just returned from a week's stay in Esterillos Oeste, and it was incredible. The house ended up being great for our family. I didn't have a good sense of the layout from the listing, but the main "house" is a motel-style building containing just the 3 bedrooms and two bathrooms, but note that the third bedroom (on the far right in the pics) does not actually connect to the other two inside. It was pretty hot last week, and the a/c in the rooms couldn't totally keep up, but with the fans going, it ended up being fine. The kitchen, or "rancho," is a completely separate structure with a large shaded patio for dining. It's right off the beach, so between the shade and the breeze off the beach, it was pretty comfortable even when it was 90 degrees outside. The guesthouse is behind the main house; it's a more modern structure with better a/c and a small living area, but it's all upstairs above the owner's garage. So, there's not much indoor living space.
But, no one goes to Costa Rica to sit around indoors; we just spent 100% of our time outside. The main pool is beautiful, with a nice breeze off the beach, and shade in the afternoon. There's a gate leading from the pool/rancho area through a small grove of palm trees straight to the beach, which is wide and stunningly gorgeous. The surf is a little rough for small children to swim, but they can dig and splash in the shallow part for hours. And the local mermaid is almost a straight shot from the house.
Esterillos Oeste itself is small and fairly quiet - we had the beach to ourselves most days - but there was a small supermarket just up the street with the essentials, and two restaurants just a short stroll down the beach (we recommend the Hotel Rancho Coral!). It's only 20 minutes south of Jaco which has a bigger grocery store, and we made a day trip to Manuel Antonio, which is about an hour drive.
Felipe, the property manager, was *super* responsive all week (even though his wife had a baby in the middle of our stay!) and couldn't have made us feel more welcomed.
Thanks for a wonderful family vacation!!