I suspect that once a few months have passed and you are accustomed to your workouts, you will find you tend to adopt a less sedentery lifestyle anyway.
I do between 7 1/2 and 9 hours of dance class a week, along with some light weights and lots of walking (averaging 2 miles a day). I love this level of activity and have no trouble maintaining it.
Before, I began my weight loss journey, I was fairly sedentery. Now, when I am faced with a stairs and escalator combination, I take the stairs, because it's faster for me, and it is so easy now. I rarely take an elevator unless I'm going up several flights, partly because it's often faster to use the stairs, and partly I enjoy the feeling I get from the light activity.
Basically, once you are more fit, you will probably find you move more in your daily life anyway - it just seems so easy to do things that once left you winded or fatigued. It's just getting over the initial hump that's hard!
BP