Undesired to eat

If the fever is gone and the child otherwise feels fine I wouldn't worry too much about not eating for a few days. Lack of desire to eat is often the bodies way of indicating that it needs a break. After a fever it is fairly clear the body has been working to clear something out of the system and taking in food weakens this process as energy is diverted to digestion, etc.

So long as the child can remain hydrated, he will most likely get his appetite back within a week. If not, you can use some general points such as CV 12, CV 6, ST 36, LI 11, etc. to stimulate the stomach/spleen system. So long as the fever is entirely cleared, using moxibustion on ST 36 will help to build the energy, appetite, and immune system.