Hi and Welcome!
There is no "official" Disney site about Photo Pass, but one of the users on this message board has a wonderful page about Photo Pass and the Grand Floridian Photo Session at
www.stitchkingdom.com/photopass
This is the info on the Grand Floridian shoot specifically:
Grand Floridian Photo Shoot - You can arrange for a private photo session with a Disney PhotoPass photographer at the Grand Floridian Resort. The session includes around 40 photos taken around the picturesque resort and its beach. Pricing is as follows: $49.95 for a Disney's PhotoPass card containing your photos which can then be added to your disneyphotopass.com account; $124.95 (or save 20% by pre-ordering - see details below) which will get you a PhotoCD with your images. If you choose to get the PhotoCD, you can save your receipt and CD and exchange it later on during your vacation for a new PhotoCD containing all of your Disney's PhotoPass images. The only catch is you won't be able to make enhancements to any of the photos; or bring the required proof that you pre-ordered the PhotoCD and the cost is only $25. Reports from guests who have participated in the photo sessions are overwhelmingly positive. Call 407-824-1700 to make reservations up to 30 days in advance or for additional information. These sessions may be extended to other deluxe level resorts in the future.
So basically, if you pre-order a photopass the sitting fee is $25. If you don't preorder, it's $49.95
As for location, from what I read, you can direct your photographer as to where you want your pictures taken. You can take them on the beach or anywhere on the GF lawns..even inside if you choose. As is mentioned above, there is a good chance the sessions will be extended to other deluxe resorts soon. The rumor is that the next one will be the Poly.
Hope this helps..good luck and enjoy!