If I may, I would suggest going with something at least 11 foot long, and with some form of a keel along the rear section. 12-13 foot would be better IMO for bigger waters that may have decent chop or wind. If you plan to surf, or run creek rapids than that's a different story.
Short flat bottom kayaks actually function better and safer in those conditions.
With the shorter yaks, you will exspend a lot of energy just keeping the dang thing going straight between strokes. Add wind, chop, swells, and/or current and those boats are a handful, and quickly become not fun. Sure they are physically lighter, and shorter for storage reasons, but where does it matter most? On the water, right? Loading and storage are only part of the equation. If you are not happy with the control, or stability of a said kayak it will spend more time at home than otherwise being used.
Be sure to explore the option of buying two different brands, styles or lengths between you and your wife. One kayak does not fit all. Most kayak shops that are near water, will allow for demos. I highly recommend do so, to get a good feel for several models. Make sure she likes what she is paddling, even if you don't find that model good for you. Nobody will think anything of it if you show up to the water with two completely different kayaks.
My suggestions are as follows (no particular order):
Ocean Kayak Scrambler 11
Ocean Kayak Caper
Ocean Kayak Trident 11
Ocean Kayak Trident 13 (I have this one, and love it)
Ocean Kayak Prowler 13
Malibu Stealth 12
Wilderness Systems Tarpon 120
Wilderness Systems Ride 135
Now if you wanted to spend a bit more and have the option to pedal or paddle:
Hobie Revolution (I have this as well, and love it even more!)
If you like fishing along with touring around scenic water holes, there are plenty of kayaks out there that are designed with fishing in mind. Many of them listed above!