Are you summoning the snake (via Summon Monster or some such)? It's a little unclear where you're planning on getting the snake from. You could always go Druid, and just BE the snake.
As far as Tripping goes, you could try to optimize Bigby's Tripping Hand, but tripping as a combat maneuver suffers from all kinds of issues (size, # of feet, etc.). Again, go Druid & summon wolves if you want to trip.