I'm sure this child is quite a nice kid, and of course you should not deliberately want to make any child sad, but let's face it...you can't stop doing things just because it makes a kid cry.
Let the vegetarians have their own reasons for not eating meat - but you shouldn't feel obligated to go "D'oh! Eating meat makes this little boy cry, so therefore eating meat is wrong!" That's absurd, really.
That being said, here are the reasons I eat meat: 1) It tastes damn good. 2) I consider it safe. 3) It's not immoral - animals kill each other for food, so why shouldn't we? 4) Did I mention it tastes good?
Now of course this does not mean we should deliberately make animals suffer either. I would be all for a method that immediately and painlessly causes an animal's death so that they are not mistreated in the process of meat preparation. But that's another matter entirely. In the end...we, as meat eaters, are simply fulfilling our role in the food chain. I see no reason whatsoever to feel guilty. It's just the order of things, as it were.