Hi Gavin, and welcome. Congratulations on finding your way here. I hope Karen does, too.
In terms of what to do and when, a lot will depend on your team's treatment recommendation, and there is a large number of variables depending on the subtype and extent of the tumour.
In the meantime, try researching Otis retreats in your area, to see what might be available. These a free stays offered to those going through Breast cancer treatment, and there is something available in all states. If nothing else, it could give you an idea of something to do.
Becareful to listen to what Karen wants & needs. She may just want to keep busy for the moment until you know more about what might happen, or she might want to retreat from everything, and everyone. She may fall anywhere in between.
How old are your kids? It's probably worth mentioning here that I don't have any, so definitely no expert.
I would say that honesty in all your emotions is important. One thing I will also say is that endless positivity from those around you can be wearing,, and it led me to hide my emotions from family and friends. Sometimes you just have a bad day, for no discernible reason
I'm sure I could go on, but also sure that there will be plenty of others along to offer support