A 3-year-old girl from Delhi is referred to the ophthalmology department after her father noticed a white reflex in both eyes during a family photograph taken 2 months ago. On examination, visual acuity is 6/18 in both eyes. Intraocular pressures are normal (14 mmHg bilaterally). Dilated fundoscopy reveals a small white mass in the superotemporal quadrant of the right eye and a larger mass with vitreous seeding in the left eye. Genetic testing confirms a germline RB1 mutation. The child's mother is asymptomatic with normal eye examination. What is the most appropriate initial management for this child?