Well... understanding that you've not asked for C&C, I think there are some issues with this image that need pointing out. First of all, was this a paid shoot? I hope not.
The good: A nice composition and a good arrangement of the subjects.
The not so good: Does he ever get tired of walking around with that tree growign out of his head?

ALWAYS be cognizant of your background details, especially in parks! The overall exposure isn't too bad, but you desparately needed fill light here to reduce the dynamic range and properly illuminate the family. You have bright/blown highlights in the background which are taking the eye away from the subject, and raccoon eyes in both mom and dad. A big reflector or OCF would have taken care of this.
Your WB is off the chart; I'm guessing it's somewhere up around 7000K, that needs to be dropped way down.
Your subjects are soft; I'm not quite sure where the point of focus was, but I don't see one sharp set of eyes. Always check your DoF tables to ensure that your aperture provides sufficient DoF for the situation, and use a shutter-speed high enough to ensure that there is no motion blur. Here, 1/125 would have done.
The small details are important too; notice the way stray hair on her shoulder make it look like she has varicose veins? Always make a last minute check for thise things.
It's a good start... head back and try for round two!
Just my $00.02 worth - your mileage may vary.
~John