As answered
previously, it is non-standard usage to use '
siempre' this way, but our friend from Argentina also pointed out that it could be regional usage. Regional usage makes it possible to use non-standard Spanish, but as Angelica mentioned, that phrase won't mean the same thing elsewhere.
Telling a child to go to a certain place using '
siempre' seems like it might plant the idea that there should be no deviation from the stated destination, in case the child's mind should wander en route.