Just read on. Computer hardware makers and furniture makers are way behind on this one. Kids are still using adult-sized computers on table tops that are too high. Only consumers can push manufacturers toward kid-sized ergonomic setups. Kids wear kid shoes, so they should use kid-sized keyboards, and so on.
Inadequate circulation sets up the hands for strain.
Children should prehydrate by drinking juice or water before computing. This helps open the microcirculation to the hands. Fingerless gloves can be helpful. Those with poor posture are at risk. I have videotaped my children to show their postures to them.