If you choose to dive Key Large (highly recommended) I would recommend Brent at Blue Water Divers.
http://www.bluewaterdiver.net/
I dove two days with them last year, and it was a very nice experience. ConchRepublic also comes highly recommended, but I have not dove with them.
http://www.conchrepublicdivers.com/
Most boat can do whatever diving you like, but at this point they may have dive plans on the schedule, so you would have to contact them to see what they have on the books.
Most dive OPS in the Largo area offer one of three choices. Wreck/Wreck, Wreck/Reef, or Reef/Reef. The reefs in Largo are very lovely and generally shallow with most ops putting you down on Reefs that range from 40'~15' depending on the sit. The Wrecks range in depth from shallow like the Benwood or City of Washington, to Deeper like the Grove, or Bibb. Most DiveOps in the upper keys will required an Advance Cert or proof of recent deep experience to dive the deeper Wrecks. Some will ONLY accept an Advanced Cert.
The reefs all vary, but most are packed with marine life, and at those depths the colors are generally awesome depending on the Vis. On a good day, you have 100' of Vis in the Largo area, and the currents are generally mild, but can vary.
As Jenny indicated the Scubaboard Invasion is planned for July 14th~16th, so the Ops I list above are rather booked up from Friday PM through Sunday PM, but there are some dives available even on those day with these OPS.
There is a party on Saturday night that should prove to be REALLY fun, with 50+ scubaboard members and staff from all over the states, and even some from overseas in attendance.
SB divers are fun, and very good divers, so you'd find yourself in good company.
Have a great trip, and hope this all helps!