Beginner needing help with cropping

I have taken this photo of my son at the park. I am a beginner to photography and I am having a tough time cropping this photo. I can't seem to get the ratio's correct. I like the colors behind him and I like seeing his hand planted on his left side, so any advice that you could give would be great.

Also, any advice on something that you see that I could be doing wrong is greatly appreciated. Like I said I am a beginner and want to improve.

Thanks

I think more important than your concern about cropping is the composition. You've got a really nice shot, with a great expression and excellent exposure and colors. Tipping the camera down just a bit would have put his right hand and left fingers in the frame, losing some unneeded space at the top. Cute photo.