I would honestly play Tate until I see some real production from CJ. I've owned CJ in the past and he has a very high ceiling, but also a very low floor depending on the defense he is playing. Denver should allow CJ to go off especially with a respectful passing threat from Britt and Washington, but Tate is the main man for the Texans now and has two good weeks in the books already. In addition, Tate will not have to share the ball as much in week 3 with Ward and Foster sidelined. Slaton will be in the mix, but I personally am not worried about him much. I wouldn't argue with you either way though if you decided to play CJ though.
10 Team QB Flex 1PPR - Week 3
QB: M. Stafford, J. Flacco
RB: C. Johnson, D. Murray, D. Sproles, CJ Spiller, M. Leshoure
WR: J. Jones, E. Decker, A. Brown, P. Garcon, B. Lafell
TE: J. Finley, M. Bennett
K: D. Akers