"The strange kids" would be ok, right? But I suppose it depends on the context, and with isolated sentences there is no context.
I still have a conflict with this adjective. Being 'ξένο' both 'foreign' and 'strange', AND having as well 'περίεργο' for both 'curious' and 'strange'.
ξένος, adj. is 1 foreign 2 strange in the sense of belonging to other people, unknown (άγνωστος) 3. irrelevant (άσχετος) I suggest: foreign children or unknown children
περίεργος is 1 curios to learn, to know 2. curious, indiscrete 3 curious (παράξενος) strange like funny looking or odd or queer
note ξένος and παράξενος = too much ξένος, that is very strange, peculiar, eccentric