Welcome to the Cafe. Hope you stick around
As for your situation, I would shoot for a value pick at RB like a McCoy/Mendenhall. Those types are still good RB1's and production-wise will be hard to replace with your 3rd and 4th round picks. If anyone goes If Vick, Rodgers, AJ etc in the first round you could see yourself ending up with one of those RBs and a Calvin/Roddy. A great start to your overall depth.
Of course, if it goes RB all the way down and you aren't all that excited about who is available at that point, do as you suggested above and go with two elite WRs and fill up on RB afterwards.
Whatever you do...don't waste those early bookend picks on a QB. The difference between Rodgers and a Ryan/Schaub is only about 40 points...and you can wait until the 7th to get either one.