Well it's a tough one. Reading about Gates having to get back into "game shape" sounds a bit worrisome but then again it's the same team so shouldn't be too bad. Also it's Virgil Green ahead of him, so once he's back, do expect he'll be mainly red zone threat. That's about it. Now if Cole/Gordon are somehow both covered, then Gates definitely will see some ball. But remember he's 38 as well.
Kittle had that shoulder separation so I'm iffy on him. He's definitely their TE going down the road but apparently he may share snaps Game 1 with Celek. Not much of an issue, probably just to ease him back in.
As much as I want to say go with Gates because of the red zone targets, I'mma go with Kittle just because McKinnon is done for the year (though Morris is a decent back up), I think Jimmy G will target Kittle more down the road.