To accomplish this, you create  one master project  with the 3 to 5 projects as sub-projects.
 Then you can generate reports on all sub-projects ( Reports->Report on entire project) or on each individual sub-project (Reports->Report from this level down). Notice that there are more in-depth reports under the Analysis menu.
You can allow the participants to see only the project they are working on via the reports, as mentioned above, or you can export the sub-project in questions (File->Export...->Subproject...).