Up thread I posted about having hot drinks made to kids temp to avoid issues. He told me it doesn't always happen. Another example: If you order a drink requiring added flavor, and they only realize half a pump in that it's the wrong (possibly not kosher) one, they most likely will not start over. At best they'll pour it out and use the same cup. I'm sure the list goes on. Being someone who deals with this (in a kosher environment) regularly, I can imagine many other situations that you would never realize.
I'm not sure about the kids temperature thing, that sounds like iffy from the start.
As far as any other concerns, there are many poskem who say it is OK.
I want to hear a concern that a posek said it OK, and a reason that makes his understanding false.