There is just something about the sound of passing gas that makes us naturally want to laugh. Within your private homes and amongst your family you will and may continue to handle these situations in your own way. Realize however that children take their clues from the adults in their lives so you may want to set some precedents early on.
As I always tell my children, passing gas is a normal body function. That said in American culture in particular, it is considered rude behavior in polite company.
When in the company of friends, associates or strangers it is best to ignore any obvious flatulence. This would include belching and/or burping. Most people know to say excuse me if they burp or belch loudly, but passing gas has more of a stigma and is a little trickier to navigate. If someone has passed gas and the smell is overwhelming you need not mention it or comment. If you are unable to stand the smell or feel you may embarrass the person any more than he or she already is, then excuse yourself from the room for a moment, breathe some fresh air and compose yourself.
If you are the person with gas you should try to hold it if possible until you can get to the restroom, outdoors or at least away from others. If you happen to have a slip that everyone hears you may want to say something like, "Please excuse me" or,"I apologize,It seems my stomach is upset this afternoon."