Hey Colonel,
Arian Foster is the starting running back and should see the bulk of the carries easily. I would say 15-20 carries plus a few receptions. I could see even more work, to try and keep Manning off the field. He played well in the pre-season and should be a focal point of the offense. He was solid at the end of last season, and it seems the coaching staff is confident in him.
As for the receiver situation,
I would go Nicks and Mike Williams. And then Nicks.