There is no setting where authentication can be turned off or on in the Galaxy Tab and authentication appears when you go to browse the internet for the first time.
Unfortunately authentication is quite cumbersome requiring the server name login name and password which could be quite challenging for younger children.
Testing the device over the past week has shown that the Galaxy is dropping out of the proxy at times. The only way to reconnect seems to be restart the device , sometimes several times before the device finds the proxy and browses the internet.
Another issue is that the device seems to retain the authentication in its settings and asks for renewal sometimes and other times not. In the settings can't find any rules for authentication to make changes.
The device browses quite quickly and will be interesting to see what happens when multiple devices are running from one access point.