Etiquette varies greatly depending on where you go. Some locations are very permissive of children, while other cultures have more of a “seen but not heard” attitude. Regardless of where you’re going, I’ll share my experiences about what has worked best for us (and what hasn’t) and the best way to set yourself up for success with the locals (or with the flight crew) — check back soon. Nothing will get you as far as being humble and apologetic if you can’t communicate — you’re the visitor and it isn’t their problem that you can’t speak the language. If they’re trying to help, even if it isn’t working, be appreciative.
Generally, you’ll do well if you’re trying to be polite and kind.