I only have a DC6, but was thinking that scheduling would be important. I don't have an answer , but these are just ideas and may or may not work for anyone... I'm hoping it will work for us in the long run.
We've been saying to DC work before play. So, everything else must be done, homework, etc before any fun. (unless it is an extended homework project, then that is different)
For extended projects, we say do 15 minutes of that project and then see how DC feels if DC wants to continue a little longer or continue that another day. The next day which has a set time for homework etc... do another set of minutes on it.
Depending on the project, we may say do 5 minutes of the project since DC is only 6.
I know procrastination sometimes is an issue. Also perfectionism. Also, choosing the topic or making the decision on what to do with the project etc etc. So sometimes, the first round is just to do a brain storm of ideas, then help them narrow down their choices. Sometimes the project assignment is so vague... (ugh!) ... too many choices makes it really difficult too for the children.
Sometimes there is just too much to do in life, so much they want to do, but what to do first, etc etc.
I didn't read the whole thread... so hope I didn't repeat what someone else has already said.