I think the first place you start to lose fat is really individual to the person. For me, my cheeks were about the last thing that started to slim down (and I really didn't lose much, I just have a really round face). That said, I also don't think there's anything you can really do to target your cheeks specifically.
Not much help, but I'd say probably just keep exercising so you can build muscle and burn fat, and hopefully your body will start burning fat from the right places. Since you don't have any issue with anywhere else, I imagine it wont be too long. But the difference might not be as noticeable as you'd like it to be.