The deal is... this is a LIFE change not a weight-loss change. If an excessive workout schedule does not fit into your life then it's not practical to do so!! The first time I lost my weight (yes, once upon a time) I didn't do much exercise outside of walking. You can lose the weight!!
It sounds like you have great ideas... so make sure you stick to them! (stairs, walking, etc.) Remember it's eat less, move more. Not eat less, do as much crazy exercise as possible. And those weekend Zumba classes will be more of a bonus! Maybe even get in one of the 10 minute SP videos in the morning or before bed if you are feeling like you need a little more! No one said it has to be one hour all at once!
I exercise on a regular basis because it's something I enjoy. And I am lucky enough to have the gym here at work for free! Otherwise it would be a much different story.
One more thing... you mentioned that packing food might make the nutrition more difficult... but I think the opposite! Think of it this way... it may take a little planning and preparation, but it is automatic portion control!! It may work out to your advantage!!!