Staying at Casa Luna end of April with Living Social Voucher

I'm staying at Casa Luna just outside of La Fortuna de San Carlos. I purchased the living social voucher that includes: rafting, ziplining, horseback riding.

Just wondering if anyone has any advice about what to bring, their experience and if we should think about renting a car? Our trip includes airport transfer but I don't want to fill like I'm stuck there. Thanks, any advice would be helpful!:)