Offline missions for local (couch) split screen coop?

You'll find that you'll have access to a two player Co-op for Garden or Graveyard Ops and what is typically the Multiplayer portal in each base will offer you the full variety of game modes and maps with AI team mates filling out both your own team and the opposing team; they aren't as good as real players but it's decent enough.

You won't be able to access the Mystery Portal found inside Town Hall since that's strictly online play but pretty much everything else has an "offline" equivilent.