Two Kids, a Dog and Some Mud

We have had some wonderful rain in the past few days. This makes for mud!! My kids and the dog decided to take full advantage of the muddy ground by digging a mud hole, filling it with water and making soup! Lizzy came running in yesterday afternoon saying, "Mom, we made you some soup!" Luckily no one got too dirty and how can I get mad? Mud is not a usual thing around here. For the most part the ground is just dry and hard. My children NEED to make mud pies at least once in their lives. (By the way, yes, Ben does just have a diaper on, but that is better than what he's usually wearing - nothing. He almost always takes it ALL off when he plays outside! What am I to do?)