I would second the recommendations in Jiquilillo, Padre Ramos, and Mechapa. I am a new resident of the area, and this corner of the country is rarely traveled, although it's a gem. The beaches are open and calm with beginners surf and spectacular sun sets. You will be surrounded by the 'real' Nicaragua, with unique opportunities to connect with welcoming locals. This is definitely NOT San Juan del Sur, with the Nicaraguan culture still intact and abundant. Yet you can still climb a volcano, surf, sea kayak, learn to salsa, volunteer on community projects, and catch fresh fish for dinner right in your neighborhood. People come to this area and stay for weeks. Be forewarned.
Depending on your budget, I'd recommend Rancho Esperanza, Monty's Surf Camp, or the Redwood Beach Resort. For kayaking, there's Ibis Kayaking at
www.IbisKayaking.com. The Moon will guide you too!