It was almost 20 years ago that I attended a children's ministry conference in St Louis. (The local fried ravioli was awesome!) Two things stuck in my head: 1) You don't have to be the "goofy" children's pastor, and 2) A kid's ability to concentrate on something is dependent on his age. If he's 10 years old, you can keep his attention for 10 minutes. And then you have to change it up.
I think these two things spared me, and the kids, a lot of frustration.