I'm not sure my solution/configuration is the most elegant. But for a year I have been doing as follows to fit with my network scheme and household members.
My first created user is Administrator, then Guest, then my personal account and other household accounts follow. I use the same uid scheme on my workstations so NFS derived permissions are consistent, as I use the NFS exports across my network's Linux workstations. Then I configure my orbiters to select certain users by default. My common areas, Living Room TV, Dining Room PC, etc, are set to select user Guest by default. And bedroom orbiters preselected to that user. Configure your orbiters permissions settings and your there. The Administrator account, once the other users are configured, I hide from the orbiters, and is only configured for consistency within my network, and to provide the Administrator samba share.
Not important to LinuxMCE, but I follow this same scheme, with uid's startiing at 10000 for my workstations, including Guest at 10001. This method/configuration I use, has been the same for a year or so, works well, gives me "anonymity" at common orbiters by default, and fits with other common network user schemes. This also fits with Windows Server 2003 providing Active Directory. And would fit with this feature request scheme: http://forum.linuxmce.org/index.php?topic=7839.0
The only thing I could see that you may want to integrate into the default install of LinuxMCE is maybe to configure uid 10000 as Administrator, uid 10001 as Guest, and then ask the user for their household member accounts to follow. But a individual network plan for your network would suffice.
As I read this threads comments a few more times, I get some further ideas on this subject. That may alter my user scheme. I could see use for a "household wide" or global user, that each orbiter is preselected too. That user could have security mode access. And a user would not have to be selected to change security mode. This last thought I have not deployed, as my described configuration has worked for me. This is interesting to consider options for. If advanced features, like Samba domain server is to be implemented, a consistant user scheme, with Administrator and Guest accounts will be important.