Most kids get between 50% and 80% of their lifetime sun exposure before age 18, so it’s important that parents teach their kids how to soak up sunshine safely. The American Academy of Pediatrics says on both sunny and cloudy days, for kids older than 6 months, use a sunscreen with an SPF of 15 or greater that protects against UVB and UVA rays. 

Be sure to apply enough sunscreen - about one ounce at a time. Reapply sunscreen every two hours. And watch the time children are in direct sunlight or high heat: Limit activities that last 15 minutes or more when heat or humidity are high. Take a look at other summer safety tips from AAP: http://www.aap.org/advocacy/releases/summertips.cfm