Answering your questions this evening is Dr. James W. Jefferson, Distinguished Senior Scientist for the Dean Foundation. A small percent of patients may have only recurrent episodes of mania, although some feel that if you wait long enough, a depressive episode will appear. Bipolar II includes episodes of hypomania and major depression. Hypomania is a milder form of mania. Bipolar disorder does occur in preadolescents, although it is uncommon.
Children can certainly be on medication if the benefits outweigh the risks.
Untreated bipolar disorder is no picnic. Excessive spending, partying all night, doing drugs, etc. You could take away the credit cards, or contact the crisis unit of your local mental health center to assess for danger of the situation. This may warrant involuntary detention. There is no easy answer.