Setting the Panel to disabled will not set the children to disabled. You need to disable all the children individually by setting the WebControl.Enabled property.
The following topic should have enough sample code for you to figure out how to do it.
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfsystemwebuiwebcontrolswebcontrolclassenabledtopic.asp