I really don't think you need a backup WR (even if you like too).....if someone get's hurt throughout the year then grab one off the WW (the group you listed....most will be there).....you figure you already have Colston, Evans, Hester rolling WR for you. Once Avery comes back you'll have Colston, Avery, Evans (or whoever at your WR3 spot)...which isn't great but isn't bad either. Picking up one of the FA you listed won't change that! (in fact I think it's a pretty good WR setup)!
I think you need a backup QB here since McNabb is already in question by everyone and the season hasn't even sterted yet!
I would target: Campbell or Hill out of the list you gave and then go from there!
Standard H2H 12 Team 1 Pt PPR, Start 1QB, 2RB, 2WR, 1 FLEX (RB/WR/TE), 1TE, 1K, 1 DEF