'You guys' is an American form of address. In recent years, 'you guys' has been adopted, to a limited extent, in the UK in informal situations, but if we say it we are aware that we are using an American style of speech. For children, you could possibly address them as 'girls' or 'boys', or if it's a mixed group, 'girls and boys' or 'children'. For groups of adults, we tend not to use any form of address, except in formal situations where 'Ladies', 'Gentlemen' or 'Ladies and Gentlemen' is used.

We do use 'guys' - although probably less so than Americans. We also use 'blokes', and occasionally when being very informal: 'fellas' (derived from 'fellows'). If you are being formal, or even just pretending to be be formal, 'Gentlemen' or 'Ladies and Gentlemen' is still pretty common.

Do Native English speaking countries other than the United States use "guys" ?( like "You guys", "Hello guys") If you don't use "guys", what other words do you use?