A number of important points must be considered in finding a climbing area. Not every tree is appropriate for group climbing. You need a tree with spreading branches if you plan on having a group of people in the tree at one time. Low horizontal branches are ideal in working with a beginner who is hesitant in climbing high the first time. Oak trees, especially live oaks, are a favorite choice.
Trees growing branches in a predominately vertical direction are poor choices for large groups.
These trees with limited spread will pack the climbers close together and create confusion as they try to avoid bumping into each other. Group throw ball sessions in a narrow tree create a scene of danger with considerable tension too. You'll need to find a tree in good health. This is where the advice from a professional arborist or forester will prove helpful. Dead branches and fungus growth along with other indicators of tree problems easily reveal themselves to the trained eye.