We have our book fair the entire week and have different activities planned for each day. Each day is usually a different theme, i.e. school colors, pajama day, dress-up day (this coincides with the all-school Mass and the day when parents, grandparents, etc are invited to school), clash day (find the most unattractive outfit you can), dress as your favorite storybook character, etc. Some of these we change each year, others (like dress-up day and pajama day) we do every year because they are favorites.
On one of the days, we invite parents, grandparents, friends, etc to come to school in the morning, go to mass, visit the classrooms, see a talent show (songs, readings by the older kids of their poems or essays, dances, etc) and then have lunch with the students.
On Friday, we have volleyball games in the gym with different grades playing against each other, ending with 8th graders versus teachers. Parents are always invited to play with their child's grade.
We also always plan our open house one night during CSW as a time for prospective new families to visit the school and meet the teachers. Many of our current parents (especially K and pre-K parents) come to show those families around and answer questions.
We will also have a thank-you reception for the parish members after Sunday mass at the end of CSW - our parish is very supportive of the school and we like to show our appreciation to them. It's just donuts and coffee in the school after mass, but it's something to say thank you for their support.