I think the choice of Ismail is definitley the way to go here.
1. As many pointed out Alexander is a career underachiever, isn't 100% healthy, and most likely is the #3 reciever behind Bates.
2. Gadsen is now playing secong fiddle to Chambers, and the run first offense brought to Miami by Norv Turner. I do think Gadsen will catch about 6 TD's this year, but receptions and yards should be low.
3. Ismail should produce well even if he loses time to Wayne, because of that offense.
For week 1 only, I would rate them Ismail, Alexander, Gadsen.
I have been doing this for 13 years, I hope I could help you out.