It depends what your goal is. The best words for an educated native speaker are not the best words for someone with very broken English. And do you need them to hurry up (in which case "now" help, or can they take a minute). And do you want to express anger or not? No I wouldn't say any of these phrases are exclusive or mainly for children. Something like this is more polite than any of the examples you provided, but may be a bit too advanced for someone with weak English: Could you please leave the room while I focus on work? And something like this is more suitable for expressing anger and urgency in an impolite and dictatorial way: F*** off out of here right now!

None of them are necessairly better or worse--they're all just different. Just so you know, none of them are very polite, and some of them are downright rude.