What to do about attention deficit disorder kids who are mild? How to decide whether to use medication or not?

The only reason to. Treat adhd is when it causes harmful dysfunction in the child who has it. Impairments present differently at different stages of development. Deficits in auditory short-term memory, active working memory, executive functions & compliance, related to inattention, impact academics. Impulsive/hyperactive symptoms more often impact behavior & peer interaction. Evaluation by a specialist may be needed.
ADD or ADHD. Kids are referred for evaluation in a mental health center if they are not doing good in school. The peds decide on giving the rx. Ritalin (methylphenidate) is given in small dose like 5 mg 2x/ day for mild cases and gradually increase according to kids response. They are also followed up by psychologist and neurologist.
Great question. It boils down to comparing risks to benefits. How impairing and/or distressing are the symptoms? Also, rather than thinking of starting meds as a forever "marriage", think of it as a "trial". If the med is not well tolerated doesn't and provide significant improvement, stop giving it! Despite anecdotal horror stories, there isn't any convincing evidence that a brief trial risks any permanent harm.