You are an edtech marketing expert. Develop a comprehensive digital marketing strategy for an online learning platform for kids (tutoring, courses, apps). The strategy must cover: 1) Target audience (parents), 2) Content marketing (educational tips, parenting guides), 3) Social media strategy (Facebook, Instagram, Pinterest), 4) Influencer partnerships (parent bloggers), 5) SEO for educational keywords, 6) Paid advertising (Google, social), 7) Free trials and demos, 8) Email marketing for leads, 9) Referral programs, 10) Measuring sign-ups and subscriptions. Provide examples and best practices, including COPPA compliance.