First, they aren't meant for 4 year olds. The reviews even say they aren't for young kids. My boys were 10 when they got theirs. You have to learn how to adjust the trim and manage the remote. Many of the parts are cheap and easily replacable once you figure them out. My now-13 year old can land his anywhere and sometimes uses it to play with the cat (the cat will chase it). They hold up fine to a crash into a wall or from the ceiling to the floor. They aren't meant to go much further than around a room.
Also, these little helicopters aren't meant for outdoor play at all. They're too touchy and every little gust affects them. They're for flying inside.
I wouldn't buy a remote controlled plane or helicopter for a 4 year old. I'd buy RC cars or trucks so he can work on his skills with the remote on the ground. I know that's not what you're asking, but I do have 2 boys (12 and 13 years old) and that's what I did.