If there's a way for you to stay in school then stay in school. Nothing wrong with working part time or working over the summer of course, but in the long run lifewise someone who's finished school has more options than someone who doesn't.
According to these forums you can live like a king on welfare in America, so has your mum investigated that option? I'm only half joking there, there may be something available to you, and while it probably won't be much every bit helps. As people have said the kind of stuff you're interested in takes time to get started, you may have to suck it up and get a 'hey at least it's work' type job. Pretty much everywhere that employs teens will get a lot of applications for the summer, so the sooner you get going with applying the better. Good luck!