Both of my kids use it, so far so good. My son is 9 and my girl is 7. My son started 6 months ago and my girl 3 months ago.
The technology has been around for many years and has become very popular in last few years. It is very safe. My friend\'s son started wearing them 7 years ago when he was 13. At that time his vision is -4.5 and now his vision has improved to -2.5. I think the lenses doesn\'t mean to improve the vision, but they will slow down/prevent the vision from getting worse.
5 year old may be too young though. You should have a try out. It takes some time to get adjusted to. It took my son almost an hour to put the lenses in the first time.