abrightmom,
You can choose the same project for them if desired, or you can do different projects.

I often let my boys choose from among the project options. Sometimes they choose to do the same project, and other times they choose to do a different project.

I just have the planning meeting with them on the "first" project day, as laid out in the guide, and then I typically break the task down for them so they know what to do each day for 5 days. I keep the project time each day the same as a typical DITHR lesson, so in that way the project does not take over our day.
One thing I do to keep DITHR going well throughout the year, is on the first day during our scheduled DITHR time, I just sit down with the kiddos and map out the pages they'll be reading in their Student Books and also choose a kick-off.

I count that as my first DITHR day. Then, I put the guide away and the next day we do the kick-off. As each day passes I just teach through the guide, one day at a time, and when I get to the project day, we just pick the project and map it out. Then, we put the guide away. The next day we begin the project.
The reason I mention this is that in this way, I don't have to do planning at night ahead of time but can just sit down and do it when it comes up in my DITHR time during the school day. If I need a bit of planning for DITHR in which the kiddos aren't needing to present, I send them to play or to go on to their next subject instead.

It sometimes adds a couple of days to DITHR to do it this way, but it keeps us going forward steadily and keeps me from having any planning to do in the evenings. It makes DITHR fit right within the school day, and I'm never caught unprepared.
DITHR truly can be open-and-go most days, as long as you've chosen the books to read. But, if I do come across something I'm not ready for, I just stop and plan it then and there and then do it with the kiddos the next day.
My oldest son really reaped the benefits from DITHR with a seamless transition to high school level literature. His moral discernment fars outweighs what I had book-wise when I was his age too! He actually chooses to read classic novels and enjoys himself in the process. His love of reading was truly encouraged with DITHR, and I am thankful daily for the discussions we had about literature in light of the Bible throughout his elementary and middle school years thanks to DITHR.

We'll be glad to help with any other questions you may have, as I'd love you to have a great start to DITHR.
Blessings,
Carrie