Drive on the offense, and rent something with some ground clearance. Learn to pass. You'll be doing it a lot. Don't speed unless you have to. You'll wish you had a Porsche on some of the canyon roads. On the way over to the Pacific side there's a place called Atenas.
http://www.vistaatenas.com/ this was a great bed and breakfast we found trying to find a coffee plantation. Don't be surprised if traffic backs up. Most of the major roads are two lane and kinda sketchy. We saw half of the highway just washed away. Road crews are always working. Lots of one way bridges too (some with wood planking). If stuck, buy coconut water from the ticos who will eventually come by selling plantains and chips. Make sure you have a jack and a good spare. Possibly a shovel if you get adventurous.
All inclusive would probably be in Jaco, but we just passed it. Lots of hotels, etc.. If near there, here are some places you should see ..
crocodiles near Tarcoles, amazing hiking
Parque Manuel Antonio in Quepos
the view at Villa Caletas restaurant (for you and the missus)
tons of zip lines for the kids
On the Carribean side.. Loved Puerto Viejo/Manzanillo.