The word 'let' was not in the options.
Maybe because its a command phrase? Like "go to school" doesnt have a subject, "you" is implied?
something about this sentence sounds really nice. Really sing-songy if you know what I mean
Why is они omitted?
It's implied by the 'идут'. Similar to when you'd say 'слушаете' to tell someone to 'listen', the вы or они are not always needed.
Did anyone get this right the first time? I bet not. It'd be nice to see the phrase in another context before we're asked to translate it.
... said Moses to the Pharaoh.
Пусть мои люди идят?
This made me smile
Why not - Let us go there?
Отпустить их туда. Would this be acceptable