I've read some articles on how to cool down soup without watering it down and they are pretty ridiculous to me. I remember when I was kid, my mom made soup and though an ice cube in to cool it off. Who's mom didn't, right? I did it too. Then I had a thought. What about the colorful ice cube balls someone gave me for festive looking cocktails? I throw one or two into cool the soup down at my son's request and voila, soup that won't burn the tongue. WARNING: don't use ice cubes that are too small or give to small kids that might try to eat them. I remove the ice balls after a minute or so and wash them before returning to the freezer.
You can pick these up at all kinds places, even dollar stores. Enjoy!