Algae oil is very beneficial for children. They do not need to take more or fewer capsules than adults. One capsule contains the average amount of Omega-3 recommended by leading companies and investigations. For children it makes no difference. They may be smaller, but because of their growth, they have relatively more nutrients per body weight than adults.
We don't have smaller capsules for children, unfortunately. If it is too unpleasant to swallow the capsule, please find our tips here.