It is important for you to realize that the glasses help your child to see clearly and without the glasses, your child has to strain to see things. The glasses relieve the need to focus which causes the crossing of the eyes. It is not caused by reading in dim lights or sitting close to the television. Many children will need glasses or lenses for life. Yes, contact lenses will usually work as well as glasses.
Contact lenses are more expensive and demand more attention than glasses.
When children become adolescents, they are often willing to undertake the responsibility for handling the contact lenses. The crossing is a symptom of the farsightedness. If we fixed the crossing without fixing the farsightedness then your child's eyes would turn out when the lenses are worn. Often, children who are farsighted can go without lenses for a few years but they eventually need the lenses to read as they get older. IF we straightened a three year old child's eyes without fixing the farsightedness, the eyes would turn out when the child is older and needed the lenses for school work.