Reserva Natural Atitlán is the best easy nature outing from Panajachel, set in forest just outside town. Trails cross ravines and hanging bridges, with chances to see coatis, spider monkeys, butterflies, birds, and lake views from quieter angles than the waterfront.
The reserve is close enough for a tuk-tuk ride but far enough to feel like a break from Calle Santander. Wear shoes with grip, especially in the rainy season. Families can manage the main trails; more active travellers can add the zip-line circuit if they want a louder version of the forest.