The biggest pitfall will be assembly--imagine handing a bike in a box, along with a tool kit, to some random person and asking them to assembly it.
Don't tell anyone I said this, but go to Performance and see what they have. They have a nice range of bike choices there, and I suspect their shop staff knows a little bit about bike maintenance.
Don't assume that you need to go a department store to get a bike in that price range, either. Most large makers are producing a full range of kids/teens bikes, with fairly reasonable prices.