Sadly, I have completed the 3 days treatment? What else can be done to help him become active as soon as possible.

You're right. Each children sachet containing Artesunate 50 mg and Amodiaquine base 150 mg should be dissolved in 30 mL clean water and taken daily for 3 days.
Although, You should stop the treatment and consult immediately a doctor or a pharmacist in case of headache, dizziness, visual disturbances, convulsions. These symptoms usually indicate an overdosage.