[/COLOR]To be honest there are none. Or no respectable operation will let divers just jump in the water on their own. 1. they dont know the area, dont know the currents or the dive sites in any way. A divemaster may be only half your age but he will have done 100s of dives in that location compared to your zero. What you need is an experienced dive master above 40 who can just take care of you and you wife. He can let you do your thing but just be there to guide you to the correct pick up location at the correct time but at your own pace. I agree many young dive masters see it as them running a tour rather than an explore as we all want different things form a dive. What I would do will be do a live aboard but ask for your own experienced guide. This way the boat will take you too different locations for each dive but your "group" will be you and your wife with 1 d/m just for you. On live aboards that visit many locations have to have set times in and out so they can hit certain locations when the tide is slack. By delaying departure from some locations will mean the next location will be reached too late as some sites are not good when there is strong current. This is why you need a dive master for you so you can not be part of a group, go at your own pace, the d/m can let you get the best of a dive site and by not being a kid will make sure the exit points and times are correct for you to not delay the boat or for you to be rushed.
Similan Islands Liveaboard. Talk with these guys and just ask for and experienced instructor to go with you. Its will only cost a small amount extra for a private guide and make a huge difference believe me.