We’re going to start this answer out by saying we strongly recommend you talk to a rabbi about this issue.
Shiva technically means “seven” and by definition lasts for seven Jewish calendar days starting immediately after the interment (burial). There are many important reasons for this first period of official mourning, but due to various considerations such as family needing to return to their homes in other cities or changes in religious observance, many families sit shiva for fewer than seven days. The length of this observance is now often determined by each family based on their needs.
You can find more extensive details about this and other Jewish funeral practices on our Jewish Resources page. We also have a helpful page on how to set up a shiva house.
Have you seen this new resource page with suggestions for setting up a shiva house? Several people asked us for such a list and so we put on as many recommendations as possible, including thoughts for how to help the family during the shiva period (remembering medications, trash and recycling pickup, grocery shopping, etc). The most important thing we can suggest is that you find one person to manage the tasks and a few others to whom that person can delegate.
If you have anything to add, please let us know in the comments section below.