Hmm la fortuna to jaco is a long drive time. There’s plenty other options available so not spending too much time in the car.
Look up la leona waterfall near Liberia. That’s a walk through the jungle and through river (footwear required that can get wet) followed by pulling yourself up a rope with rock faces on both sides in a little canyon to see the waterfall. It’s pretty cool.
Finca la amistad is a wonderful place to stay. Lots of toucans and sloths on a chocolate finca. Making your own chocolate is always a crowd and stomach pleaser!
If intending to go to Jaco as last stop, detour to Monteverde is a must. If not, then consider replacing beach time at flamingo and Conchal/potrero area for a spot of fishing, diving or sailing. Plenty sunset cruises but if you sail and want to take your own boat out, there’s a sailing center in surfside (brewery there takes bitcoin!).
Before finalising any plans though, look up if the turtles likely to be around and shake everything up for that spectacle!