Our stay at Los Altos we were charged for an extra person/bedroom but they opened all 3 bedrooms. The man who checked us in was like 'if you book through Hyatt, you get all 3'
We gave DS his choice. Lol. The master is huge with en-suite bathroom. There is a bathroom for the other 2 bedrooms to share and a powder room. The place is huge and includes a full kitchen. They sell as condos, you can buy one for $700k.
DS has been to CR at ages 3 and 14. Plenty to do. We have never rented a car, on vacation neither of us wants the stress of driving. Last March we stayed part of the week in Guanacaste at Hyatt Andaz Papagayo and the other part in Manuel Antonio. Both are on the west coast. The only areas of CR I wouldn't spend much time in are Limon (very touristy and some crime due to being a cruise ship stop) and San Jose (very urban, lots to do but also higher crime but not the CR vibe we prefer) The international airports are in Liberia (more northern) and San Jose and both will require a drive to any resort areas.
In Guanacaste there are lots of tours involving animal sightings, short hikes, boat tours. Many resorts in the area are high end, some all inclusive. The Andaz was beautiful, nice beach and pool but nothing nearby so unless you drive or hire a driver you eat on property for all meals which was quite expensive. Guanacaste to me is very 'resorty.' Manuel Antonio has a huge national park which has more wildlife than you are likely to see elsewhere. We hiked the park, did a sunset sailboat cruise and toured a small plantation that grew coffee & vanilla. There are loads of tours on Viator and the Chase portal, maybe look to see what things you think you might enjoy and narrow down where to stay based on what there is to do. We booked all activities through the Chase portal. Los Altos is in a small town, so you can walk to shops or restaurant. The beach at the resort is small and quite a walk (the resort in built on a hill/cliff with the beach at the bottom) or they will drive you. There is one restaurant, with free breakfast, that also gives a cooking lesson on empanadas. There is a small grocery near by where you can buy a few things.
You are used to FL, so weather probably not an issue, but March is dry season in CR and we had weather in mid 80s to low 90s the last week of March.