Depends on what RB's are on the board at 5. If any of Bell, AP, Lacy, Charles or Lynch are there I think you have to consider. If all of those RB's are gone I might look at Antonio Brown. I typically wait until round 3 or 4 to take a QB (Big Ben, Cam, Brady, Wilson). If you do need to take a WR in round one, I would recommend going RB with 2 of your next 3 picks.
My league is the exact same rules/number of teams as yours. I draft 8/10 soon.