Just had a look where we went, We met my daughter, hubby and two kids(1 & 3) out there in jan17(not16 as I said) it was an end of maternity leave blowout, Giles is a surfer and it is a must do apparently.
They had 10 days in Domincal in a national park, they said it was amazing, not quite so developed, then we met them in Arenal for the volcanoes, stunning if it’s not raining and low cloud which it does a fair bit!!
We then all went to Santa Teresa and Nosara for a week at each, we had a house in each, they are 200km apart but 4+ hour drive, both nice places with long beaches ok for surfing and swimming, beach bars, restaurants, sunsets etc.
Once you get away from San Jose the roads change dramatically and road signs are a rarity, sat navs are an expensive extra on hire cars!! 4x4 are recommended because of the state of some of the roads(we managed without but it was rough in places), plenty of waterfalls just off lots of roads and abundant wildlife, toucans, coatimundi and various monkeys.
It is a stunning country to visit and safe(for Central America) but we did get through a lot of cash
Enjoy.
Al.