What are ways to treat dental cavities in children?

Good fillings. Decay removal, agood base to protect the pulp, and a proper filling are necessary.
Fillings. Many times the best treatment is a filling, but this does not mean that is the only answer. Sometimes, of it is a baby tooth and the circumstances are right, we would remove the tooth. Other times, a Fluoride treatment can help. Most of the time it is a filling. The best treatment is prevention!
Depends. Are you asking how to fix the actual teeth or how to perform treatment on the child with regard to behavior? The process of fixing teeth is mostly the same in children and on primary teeth. With regard to behavior and cooperation, most children do just fine. If there is an issue, then one can consider nitrous oxide (laughing gas) or other forms of sedation to eliminate apprehension or fear.