Audiobooks discussion

Which should I start with. I downloaded the hobbit but I'm thinking of returning it, it seems too childlike.

Absolutely listen to the Hobbit first. While The Fellowship of the Ring gives sufficient background to be going on with, LotR builds on the ground first ploughed by The Hobbit. Yes, The Hobbit is more childish, it was invented as a bedtime story for Tolkien's kids, but it introduces much of Middle Earth and many of its characters. You will pass by some of the same territory in LotR that was experienced by Bilbo in The Hobbit and the references to the places or things that happened there will mean more if you've read it. Also, Ingliss narrates all four books and the tunes he uses in The Hobit are repeated for similar or same songs in LotR. Also, I think the first chapter in Fellowship will be more meaningful if you understand hobbits, as gleaned from The Hobbit itself. Many find the first chapter in Fellowship almost incomprehensible at times or merely silly if you haven't been versed in hobbits first. No matter what, it's worth it!