Boys on swing at carnival outside Brevnov Monastery

The one thing I don't like about this photo is the lack of contrast -- it doesn't "pop". Any suggestions on how to make the whites whiter while keeping the blacks black? I'm afraid that if I stop up to bring out the whites, I'll end up with greys in the shadows instead of blacks.

 

I'm new to photography, so any help is appreciated.

First or all its a good shot, do some cropping, there are a lot of lines here, play around with photoshop or the like, look at curves, you can almost do what ever you want