A native English speaker would not have included "together" in this sentence.
"Together" is indeed superfluous. I wonder whether it's a matter of the Duo creators wanting us to understand the literal translation, or simply another example of the rampant Chinglish in this course.
I think the course creators are having trouble thinking of English sentences where we really would use "together".
Would 和 be acceptable instead of 跟 (请让我和你一起去) ?
Yeah they should both be fine.