lol, be careful about asking about kids and computers, opens up a whole can 'o worms!
http://forums.overclockers.co.uk/showthread.php?t=17672748
As for your question, i use content protect now, its pretty good for the internet side of things, as for locking away the control panel and such -
Make sure your kids logon is limited user (sorry if thats teaching you to suck eggs!)
type "gpedit.msc" into the run dialog
go to Administrative Templates->Start Menu and Task Bar
in the left window you can choose what to disable or hide, just right click on the one you want and set to enabled.
the downside i've found with this is that whatever you disable is disabled for every user, even your admin logon. this can be a pain obviously.
to remove items from the start bar for individual users, right click the start bar when you are logged in as that user and goto properties
click the start menu tab, then click customise. this will give you a list of everything in the start menu that you can disable for that user.
The problem with this is that if your kids smart enough to find this menu, they can change it back.
If anyone knows how to disable the properties menu for the start bar that would be handy