A day at the Park

I Love the outdoors and my baby enjoys it when we get to go to a park and spend a couple of hours running around. I usually take some toys with me but now I have started to notice how sometimes that can become more of a problem than a good idea. I am guessing sharing is probably the toughest lesson to teach the children, but when it turns into a fight, I wonder, is the child or the parent to blame? How long should we wait to say something or should we just simply remove our little one from the situation?