Add shrimp to medium glass bowl; add Ceviche, making sure all shrimp are completely submerged. Cover bowl and transfer to refrigerator. Marinate until shrimp is pink and opaque through center, at least 24 hours, and up to 48 hours.
Stir avocado and cilantro into shrimp mixture; divide shrimp and some marinating liquid evenly among serving glasses. Serve with plantain chips.