Hi Steve,
Diving in Thailand is best from liveaboards as you can reach sites not possible by daytrips.
If you are here for 10 to 12 nights then I suggest a 7 day and night charter for your group to the both the north and south andaman. This would include Phi Phi, Koh Haa, Hin Daeng and Muang, the Similan islands, Koh Bon, Tachai and Richelieu Rock.
You can follow this with a few days at a beach resort to complete site seeing and relax before traveling home.
You can contact us directly if you want to arrange it with us at info@scubacat.com or look at the website on www.scubacat.com