Of course, the hard part of serving soup to the under-7 crowd is the whole its-too-hot thing. Blowing on the soup really doesn't alter the temperature much and for some reason my four year old hates an ice cube floating in his soup almost as much as he dislikes a blistered lip.
One day, as I was reaching into the freezer for an ice cube to melt in his soup before he noticed, I had a moment of sheer mommy brilliance. Frozen veggies! Instead of grabbing an ice cube I grabbed a small handful of peas and carrots. I didn't add enough peas an carrots to turn the soup into vegetable soup, of course, but just enough to cool it down a bit. And what mommy doesn't like the I'm-sneaking-in-a-few-more-veggies moment?