...'to kill two birds with one stone' is plainly not nice; it's outdated, sending kids the negative message, almost impossible to do, and you disrespect the law if you set out to try the feat on some birdies that most likely may happen to be of a protected species... why not be creative when the occasion to use the expression arises and make up your own...like I'll use 'to sing to two frogs with one note'... 

'to kill a mockingbird': now that's another thing sticking in my craw on this beautiful summer's night...