If you find it difficult to stand for long periods because of your feet, how about trying chair workouts ? Coach Nicole has a couple of different cardiovascular workouts that can be done while sitting in a chair. www.sparkpeople.com/resource/videos-detail
when you're done trying these, do a search on YOUTUBE for chair workouts or chair aerobics. there are some very vigorous workouts that can be done while sitting in a chair. they have even have chair yoga workouts too.
Do you have access to a gym with a pool ? You might also try swimming or water aerobics. being in the water will take stress off your joints and feet. Another option if you have a gym member you might also try a recumbent cycle. that's the bike where you peddle in a reclined position. that takes stress off the feet too.