Rookies aren't bad. Rookie WRs, however, are the biggest gamble. I nabbed Blackmon in the 11th or 12th so I figured it was a low-risk, high-reward pick. However, he likely won't help my very thin WR corps. All of my WR targets were picked a bit earlier than I had experienced in mocks. And for some reason, someone picked Toby Gerhart in the sixth, preventing me from locking up Peterson.
You have a nice team. Carson will do just fine for the one week you need him. Just keep an eye on the waiver wire for a streaking QB if you're uncomfortable with him. Your RBs are your weak suit but someone sitting ontop the trash heap always gets hot and will be available on the waiver wire.