Johnson and Nicks, or Manningham if Nicks doesn't play. Since Tebow began starting, Decker's only a good option if he catches a TD, and that's too difficult to predict. He just hasn't gotten much yardage...
Helu at flex is an acceptable play. You know the risks, I'm sure:
1) Shanahan is his coach, so he may not even get to play.
2) MIA is actually very good against the run. OTOH, Helu proved last week that he was a good checkdown option, so he could have another big day through the air, turning short passes into long gains.
It's hard to make any suggestion without knowing your other options...
12 team, H2H, Standard Scoring (Starters in bold)
QB: P. Manning, Luck
WR: Julio Jones, Welker, Alexander, Hilton, Shorts
RB: Rice, Wilson, BJGE, LeShoure
DEF: DET, SD