Costa Rica for sure with young teens - you’ll all love it!
Monteverde for cloudforests, ziplining and beautiful lodges
Manuel Antonio for hiking a beautiful national park with fabulous beach
Tortuguero for rustic Caribbean village, adventurous to get to and depending on time of year, you might see turtles nesting on the beach
Vincon de la vieja for Volcanoes. Waterfalls and empty dry forest
Arenal for active volcano, hot thermal pools in nature
Lots of resort type hotels on pacific coast… more rustic accommodation on Caribbean coast (both can be bit rough- good for surfing !)
You will see diverse range of animals and plants everywhere, food is fresh and healthy, it’s fairly safe (petty crime like anywhere else but not dangerous like other countries in Central America)
If you’re feeling more confident head over to Nicaragua (also pretty safe) - better roads than Costa Rica
BUT if you like history and architecture then Costa Rica is not for you!