If you book packages including diving and accommodation you usually get quite good rates...for more diving!
The best spots for experienced divers (that means AOWD certified and up) are certainly Cats and Bats (but it costs more to get there), most popular local dive sites are Virador, Monkey Head, Punta Argentina, Toruga and Punta Gorda.
Very important and sorry to say, October is usually the worst month for diving the Pacific side of Costa Rica, Caribbean side seems to be a better choice during this month...
About 1/2 h from Playas del Coco you have the Congo trail Canopy, 35$, which is fun! Unfortunately while zipping through the trees, it's hard to see the wildlife, but they have a serpentarium, butterflyfarm and some monkeys at the end of the tour (I think they charge 5$ to see all this).
There's another tour close by offering all in one for 80$, meaning a canopy tour, a river float and a horse back ride with lunch or dinner, all in about 1/2 day. This tour certainly allows you to see wild life in its natural habitat: crocodiles, water birds, monkeys, ect.
About 1.5h away (transportation is best in a rental car...) you have the Rincon de la Vieja National Park. Besides visiting the volcanic park to see its activity you have choices of rapelling, canopy, canyoning, horseback, ect.
Hope this helps