"Astute" is a postive connotation. It means to be perseptive, sharp, clever, etc. I have never heard it used with a negative meaning. However, with sarcasm, nearly anything can take on a negative tone. But that doesn't mean that the word has a negative connotation on its own. Hope this helps!
It was either the third statement or the last one that I would have chosen. I believe "we laughed at the dog with the shaggy fur who was catching the ball" would be the best, however.
