Assuming you are doing a Liveaboard you have three main choices:
1. Wrecks & Reefs (or Northern Egyptian Red Sea) don't be put off by wrecks in the title, there are plenty of reefs and the wrecks all have lots of marine life. My wife isn't a fan of wreck diving but we have done this route a couple of times and she has always enjoyed it. In fact lots of the wrecks are more like reefs now. Generally fairly easy diving, so good for any experience level. A nice mixture of reef types. Unlikely to see sharks on this route at this time of year, although I have seen one or two in October. If you want to do night dives these will be available every night. I think this route gives the best introduction into the Red Sea and is a fairly relaxed week of diving.
2. B-D-E. Basically a journey around the sites of Brothers, Daedalus and Elphinstone. A reasonable amount of experience is needed for this route, and there will be a couple of overnight crossings. Weather in September should be calm, but sea conditions can be rough at any time of year. Nearly all the dives are deep wall dives with great coral and marine life. A good chance of seeing sharks. Maybe a chance for a night dive at the start or end of the trip. I have done this route a few times and I heading back this year in October again.
3. St Johns. This is the area south from Marsa Alam. Generally fairly easy, with very pretty reef dives. Normally sheltered crossings overnight. A slim chance of seeing sharks. I have dived this area a few times and do find all the dives sites start to merge into one after a while. It isn't my favourite area, but would happily go back again.
I think the favourite route I have dived in the Red Sea is 'Brothers and North' This went from Hurghada to the Brothers, we spent two nights there before heading north to Ras Mohammed, Thistlegorm and Abu Nuhas and finally back to Hurghada. Personally I think this showed the best sites in the Egyptian Red Sea, it is just a shame that not many boats operate on this route.
Which ever route you pick the diving will be great. If you want sharks BDE is the one to go for, maybe a little early to see them, but you never know what is out there.