I rather Dak get all available snaps. If you gone roll with the kid, then roll with him all the way.
History has shown that Garrett doesn't sit his starters, so no reason to start now.
On a side note... giving Romo mop up duty? Seems insulting, but he's a team guy so he'd do it, but I'd totally feel insulted if I were him. Hell, he's already running the scout team to prep, tho.