For seven days, just very light trainings/rest would suffice.
I think you'll both make it hopefully since the time limit of 12 hours is too high.
For the Next Time: Prepare in Advance
It's just a bit longer than marathon, here is a 12-weeks training plan for marathon to give you a big picture of how the prep should look like. However, you should not ...
Here is a 12-week plan with more info on this link yet I would not recommend you to neither follow the plan nor do any ultras based on the very limited information that you've provided in your question:
Ultras are for those who can at least finish a road marathon below 3:00/3:30 hours and they have an athletic/excellent Rest Heart Rate.