While I think it's bad to tie gifts to academic performance and it's always irksome when parents drop a ton of cash for their kids, I'm with this option.
preaching/
You're 14 so you're just starting HS. You have got to start worrying about your GPA and resume. I'd start looking for academic things to do during the summer. There are a lot of research programs where you get to play lab monkey but pick stuff up as well. This kind of stuff looks way better in a college app than flipping burgers at micky-Ds.
I had friends that worked labor jobs in HS. They had cool stuff that I didn't. But I got into a good college because colleges weren't really impressed with busting 40 hours a week doing mindless stuff. As a result, they are still doing 40 hours a week (more now to make ends meet) doing mindless stuff.
I'm am all for learning to earn what you want. However, you have to be careful that you don't let your short-term goals eclipse the greater good. People are here are saying you should do anything to get your iMac, but if you keep that mentality you'll be doing anything to get the next best thing forever. Being patient and putting something off for the greater good is a virtue as well.
I'm not saying that stacking shelves is going to keep you out of college and ruin your future. I just want to temper what everyone else is saying.
So that I'm not a total kill-joy, a lot of research positions have stipends associated with them... mine was around $3000 for the summer if I recall.
/preaching