Cheap Chinese duffels with built in wheels and pull out handle weigh next to nothing and you can use them for your carry on luggage. Find it in Chinese luggage shops or big supermarkets luggage departments, the classy luggage shops dont keep them in stock. They are perfect! Dont buy anything with a heavy internal frame, the cheaper and lighter,the better for your purpose! if you dont abuse them, they should last for several trips. Pack your BCD, regulator, mask (if its prescription lenses) and costume in this and you will OK in weight (about 7kg) for carry on. Let hubbie carry a good size camera bag extra and wife biggest handbag you can manage.Dont use a strap on wheel trolley for the duffels, we tried it, its really most uncomfortable, wants to fall onits nose. Now, should you lose your checked luggage, you still have your diving essentials...in your hand luggage
Checked luggage? Well a lightweight backpack each of course - good quality this time, also weights a fraction of what a suitcase weighs. And seeing you are already carting the duffels, this lot goes on your back, easy peezy! In here - well the wetsuits, the fins, booties, toiletries, medicines, hats and suntan oil a few pieces of clothes and your full allowance of wines (good ones from home of course) a bottle of gin. Winning recipe for weight and comfort traveling...enjoy your trip!