The 4 friends are only 14 years old and they make some bad choices later on in the story. They do drugs/alcohol and other stuff... I'm trying to make my story as realistic as possible.
Sounds like a pretty good concept, however the bit I quoted is the only bit I have a problem with.
You say you're trying to make it realistic. Firstly, not all teens do drugs (and this is coming from a 17 year old). I think it'd be interesting if all of them but one did drugs, and they made fun of him for being 'scared'. Also, 14 is slightly young to start taking drugs. Yes, some of the people who start taking drugs younger may start at 14, but most, if they took them at all, would start at around 16.
I think it'd be cool if they were all different ages. What if one was 14, who started taking drugs at a young age, one was sixteen, the one who likes computers I think you mentioned, and he can be the one who doesn't do drugs, and the leader could also be sixteen but older than the other or maybe seventeen. I think it'd be kind of cool if they were a mixture of teenage ages and not all fourteen, especially if you want to make them do drugs.
Also, you may want them to come clean from drugs as the plot nears it's end, as it can show they're not as 'bad' (but you can keep them slightly rebellious) and having people who take drugs achieving something great could be frowned upon by being seen as a 'bad influence' to teens (who I assume are you target audience). I'm not saying be afraid, and you could maybe keep one doing drugs or make them 'recover' near to the end, I'm just saying you don't want parents to see your book as TOO MUCH of a bad influence.
Other than that, I think the concept sounds pretty good. J was just suggesting ideas and you don't need to take them all on board, or you don't need to listen to any of them at all, they're just suggestions.