Jennifer,
I believe this is the perfect place to introduce Dr. Nathanson's Compass of Shame concept. Like a compass with its four poles, Don observed that failing to accept the message triggering shame, people may respond in one or more of four ways to the shame experience.
The Withdrawal pole most closely resembles the basic affect of shame and is the one you mention not always seeing in your ADD children. This is also the pole that many pharmacologists have called "atypical depression"
The Avoidance pole consists of what might appear to be distractions from the shame experience. The avoidance pole is the basis underlying most addictions. The action may appear very driven or compulsive.
The Attack Self pole reactions range from mild deference on through significant self-multilation. Statements like "I'm so stupid" are seen here.
Lastly, the Attack Other pole contains the basis for prejudice and the "put downs" of others. When many people question why the SSRI meds help some anger or temper problems even when no depression is present, it is due to the down-modulation of shame in a person who has a tendency to use attack other.
I hope that this brief outline of the Compass of Shame will allow us to better see the manifestations of activation of the Shame/Humiliation affect in circumstances where the characteristic body slump and downward gaze are not present.