Take Optimal Amounts of Omega-3s. According to Dr. Newmark, kids between four and eight years old should take between1,000-1,500 mg. a day. Older kids should get 2,000-2,500 mg. daily. Look for a product that has twice the amount of EPA to DHA—the two main types of omega-3's. Liquid or capsule forms of omega-3 fatty acids are best.