I third yoga.
@gailcalled: Your situation is exceptional, and the OP does not mention any history of spinal problems or injury.
Yoga is modifiable to the individual. Not all people have the same strength, flexibility, or proportions… so the poses can be altered to your abilities. A good yogi will teach the modifications leading into the full expressions of the poses, and especially guide you if you’ve informed them of your specific challenges.
Unfortunately, not everybody has a good understanding of their own body mechanics; and many don’t realize that yoga isn’t just about relaxing and streching… you have to know which muscles to engage to properly support the stretch.
I am sure that there are some people (perhaps even you) for whom no form of yoga should be attempted, but for the vast majority, yoga is beneficial for the whole body, and spine is far less likely to go out of alignment in the first place, and if it does, you’ll know which moves will bring it back.