If you want to stay in Aus, I would suggest that in your limited time you stay on the East Coast and do one of following things;
RIBBONS
Liveboard up to the Ribbons out of Port Douglas as you suggested yourself. Excellent dives but meing stuck on a boat for a week may not be the mrs's cup of tea. The snorkeling at some of the regular dive sites is fabulous. yes, it is cyclone season so you may be unlucky. Ive only done trips up there with www.undersea.com.au.
SOUTHERN BARRIER REEF
Lady Elliot Island, off Bundaberg in Southern Queeensland. This is the most southerly reef on the Great Barrier Reef, and it is the ONLY RESORT ISLAND that offers very good Great Barrier Reef snorkeling off the beach so you and the Mrs will have a really good time. Diving - well I reckon its great. The island sits on quite a small reef, but it is out in quite deep water and the vis is usually excellent. There are boat diving and shore diving opportunities. Lady Elliot is also a loggerhead turtle rookery, and at that time of year you will probably see the last of the hatchlings leaving the beach. Mantas and leopard sharks are the oher attractions underwater. It is also a seabird rookery, including terns, noddies, quite a few nesting red-tailed tropic-birds, and lots of brown boobies around, and even a few Frigate birds. Have a look at their website. http://www.ladyelliot.com.au/ It isn't the ritz, but it had recently had a makeover with new owners. You have to fly over on a small plane and their luggage limit is ridiculous (10kg for non-divers, 20kg if you book a dive pacakeg.) They won't guarantee excess bags travel, and they mean it, but you can hire dive gear. Most of the beaches are coral rubble rather than sand.
Heron Island is another island resort right on the reef. It's a bit further north, but still southern reef (the reef is 1200km long remember). It is of a higher accommodation standard than LE but hasn't got beach snorkelling to come anywhere close to lady elliot, and there is no shore scuba (it sits on a much bigger reef) everything is boat diving and boat snorkelling, which is well organised, but a bit regimented. It is a green turtle rookery (late hatchlings again), and there are heaps of birds there too, which can be very noisy at night. It is a very pretty island and the beaches are nice. You transit to the island by high speed launch , so you can take your own dive gear. http://www.heronisland.com/.
Between those two, for diving I would say Lady Elliot, for a week off with some diving Heron is nice. Both are still in the cyclone zone, the further south you are the less likely you will be to get unlucky.
When you are in Queensland, also remember that the dive industry is over-regulated, so if you are an experienced diver, you will feel like you are being nannied somewhat.
LORD HOWE
Lord Howe. Now that is a great spot. http://www.lordhoweisland.info/ You will have a great week if you go there. Not just diving but walking and snorkeling and having a nice time together. The snorkeling is really good off some of the beaches, but the best snorkeling is from boats. Diving is from the boat too, some simple coral reef diving - great mix of fish species as the tropics and temperate species mingle, lots of diversity. Also some great "adventure" diving, schooling galapagos whalers, big seacliffs, and if the weather is right, 20kms or so south is balls pyramid, a sea stack which is a reall open ocean dive experience. Also a summer bird rookery with heaps of species. Nice thing about lord howe and your time frame is that is 1 direct flight ex Sydney or Brisbane and you are there, so you will make the most of your time.
Any of those options would give you a great weeks holiday.
darren