Hey, this was my exact team when I played for the first time! Had a Poochyena with me, too (Of course, not while I was at this part of the game. Don't think you can take third members with you...).
Good ol' Cubone tanking, alongside Chiko-Screens. All you need is Light Screen and Reflect set up while you spam Headbutt at Articuno. Get Chikorita to throw Gravelerock from the back after it sets up the screens.
As SF said, you're both weak to Ice, so make sure you keep your HP above half, or you're toast.