good.jew: I was also going to say that Nechoma may have been referring to the fact the we must turn away from a child who isn’t dressed properly when saying a bracha.
As to what you said, I disagree totally. One doesn’t need to understand the words of a bracha to know that we are saying a bracha to thank Hashem for the food He has given us, and if we don’t say the bracha it is as if we stole the food since all the food actually belongs to Hashem. A 5 year old should understand this.
what popa said: Adults don’t think about the brachos they are making either, and often don’t know what they mean either. is unfortunately too true. From observing my own children, I think 5 year olds make better brachos than most adults I know.