I'm by no means a 'fitness person,' but I can try to help
I swam before IP too! I tried keeping it up twice a week but it really slows my losses...
I do yoga classes at the gym a few times a week and I would highly recommend giving yoga a try! I love it more than any other exercise.
I haven't done a video in awhile, but I remember liking Crunch: Super Slimdown yoga/pilates with Ellen Barrett. I was able to do most of it in the 270s with not very much flexibility, so I'm guessing it might be a good match for you. I've also heard good things about Crunch's candlelight yoga, and I think that might be a little 'gentler.'
Shiva Rea is a really great instructor, too, but I haven't used too many of her videos- maybe try reading reviews on amazon or collage video?
Do you get ExerciseTV? They have some great gentle yoga rotations on, too! Otherwise, look for 'gentle,' 'hatha,' or 'beginner' yoga to start with. The videos I've tried have been pretty accurate with levels.
Good luck! I think you'll love it.