We decided to get the Flex for our kids and my wife has one as well. It has been a great way for the kids to understand how much they are or are not moving during the day. It is awesome to see them interested in how much activity, sleep, water, etc they are getting each day. In fact, having the kids wear the flex has made us more aware of their sleep quality. Something that kids don't often report on themselves. After the first night our older son's sleep data was eye opening. He was having very restless sleep. We had no idea and are very thankful we started using the flex so that we can try to help him improve his sleep quality.
The flex is more basic than other fitbits but it is perfect for our purposes. It does not track floors climbed or monitor heart rate. They are sleek, water resistant, has at least a 5 day battery life, sync easily with the app and seem very accurate.
Also appreciate how it comes with a small and large size band in each box.