Although Apple's KnowledgeBase article number 107623 claims that OS X 10.2.6 server can be set to inherit permissions or set with custom permissions, this ability seems to be less of a feature and more of a phantom. After searching the Apple Discussions, I have found many other users with similar problems, and the only solution seems to be to give up with Workgroup Manager and embrace cron. Until tonight I had never used cron, but I now understand its use. I wanted to pass on my solution to this problem to anyone else with this or a similar problem (I also posted on the Apple Discussions).
You will need a basic understanding of how to execute commands via the Terminal (specifically pico) and have a basic understanding of permissions (owner, group, others, chmod, etc...).
I ended up using the Unix command cron to run a command that fixes the permissions for my /Shared folder on a regular schedule. It sounds a little scary if you have never used cron, but trust me -- it's not difficult! My roommate showed this to me in no time. Below are annotated instructions - I hope they help. I wish Workgroup Manager was able to take care of these permissions, but it doesn't, and this is the easiest solution I could find. And believe me: it's easy! Here's what to do:
As root (use sudo) edit the file /etc/crontab (for example, sudo pico /etc/crontab and enter your root password when requested. When you open the file, you will see a page of text that looks a little intimidating. At the very top of the page are some environmental variables. If you don't know what that means, ignore them (or look them up). The first line to note is the one that reads:
#minute hour mday month wday who commandNote: Any line beginning with a # is a comment and as such will be ignored by cron. When you add a line, you will define when that command runs based on those column headings. When you open the file for the first time, you will see several examples of commands that are set to run for system maintenance. For example, the first command under the "# Run daily/weekly/monthly jobs." line is:
15 3 * * * root periodic dailyThe command called periodic is a system function used to clean up your computer. This cron line tells it to run as user root every day (that's the * under the wday for week day and mday for day of the month), of every month (that's the * under month) at 3am (it's in 24hr time) and 15 minutes: that's 3:15am every day. Get it? (A star means "every.")
[robg inserts: For a longer intro to cron, see this older hint.]
The command I am running is supposed to set permission for all files in /Shared so that the Owner and Group have read and write access. That command must be run as root. Here's the line I added:
*/1 7-19 * * * root /bin/chmod -R gu+rw /SharedThe -R is to set permissions recursively in the folder /Shared. For more options for chmod, type man chmod.
Under the minute column, I wrote */1 to have the task run every minute). I only have my command running from 7am through 7pm, so I wrote 7-19 under the hour column (remember, 7pm in 24hr time is 19).
Note: Don't forget to save the file when you are done. If you used pico, hit CTRL-X to exit, Y to commit to changes, and hit Return to confirm that you are saving to the file /etc/crontab.)
I was hesitant to solve this problem using a UNIX command, but Workgroup Manager just isn't living up to my needs. It's too bad, but I feel that OS X Server just isn't yet ready for the corporate world. Maybe 10.3 will be better. For now, though, I expect cron will make my client happy. Heck, they don't know the difference! Good luck, and I hope this helps.

