Traditionally, I take a nondirectional bias with plays since I do not know how the announcement will turn out and do not know what the market reaction to it will be. Consequently, I generally opt for a nondirectional iron condor or short strangle or, in the alternative, an iron butterly or short straddle in the event I cannot get enough "juice" out of an IC or short strangle to make the trade worthwhile. Look to take off IC's/short strangles in their entirety at 50% max profit and iron butterflies and short straddles at 25% max.
Because the Sep 11th weekly expiry would provide me with too little time to manage the trade post-earnings, I would probably opt for the Sep 18th expiry to allow time to roll for duration and credit if a side is breached.
A Sep 18th 56.5/75 short strangle: 74% POP; 1.19 credit; undefined BPE.
A Sep 18th 53.5/56.5/75/78 IC: 71% POP; .64 credit; 2.36 BPE
A Sep 18th 65.5/65.5 short straddle: 54% POP; 6.80 credit; undefined BPE.
A Sep 18th 53.5/65/65/78 Iron Butterfly: 50% POP; 6.26 credit; 6.74 BPE
Notes: I would note that the break-evens for the short straddle and iron are tighter than those of the short strangle and IC . Although the max profits of the short straddle and IB are attactive, you'll also notice that the POP%-age is much lower than that for the IC and short strangle. Generally, where a short strangle or IC gives me enough juice, those are the setups I go with. The max profit for the IC here isn't fantastic, especially if you look to take it off at 50% max profit, so my preferred setup in this case would be to go with the short strangle, assuming that I want to devote the buying power to the trade.