Use common sense and it is a lot of fun
The CommonSense review has a lot of incorrect information. The biggest myth is that you can see where other players are in real time. This is completely false. The only time you see another player's name is if they have a Pokemon at a gym. (I will mention that unlike other Pokemon products, they do not censor names, so I have seen some inappropriate user names). Basically, if you use some common sense, pay attention to your surroundings, and don't go to places you would consider unsafe ordinarily, you should be fine. I only gave it 4 stars since it is still very buggy and crashes or locks up a lot, so it can be annoying at times. But, it has gotten my 12 year old daughter out and walking, which is awesome. Plus, being able to go out and catch Pokemon yourself is pretty cool. Younger kids definitely need to have self control - if you don't trust them to not run off into the street ordinarily, probably you shouldn't let them have your phone and chase Pokemon with it. If you are confused about any of the game mechanics, there are plenty of articles around to help you figure it out. www.serebii.net is a great resource for any Pokemon related information, and has an entire section on Pokemon Go statistics. A couple more things - it really doesn't use much data. My weather app uses more data than Pokemon Go! But, it does drain the battery very quickly. The battery saver mode has the screen go dark if you hold the phone down, and it will vibrate if there is a Pokemon nearby. However, it won't let you know about PokeStops or gyms (but you can figure that out easily). Another tip - if you want to play together as a family, choose the same team so you can take over gyms together.
For those who are curious - the origin of the game was from a couple years ago when Google did an April Fools event with Google Maps, where you could find Pokemon all over the world with Google Maps. It was combined with the game Ingress, which was part of Google, and then spun off as Niantic. Ingress had players create portals all over the place - most of those locations became PokeStops and gyms. Nintendo, Google and Niantic all worked together to create Pokemon Go.