Without more information or a site link it's difficult to give you specific advise but basically you will need to disable the widgets within your existing media queries. You will also need to adjust the main content width as well for those views.
To make it even simpler you could assign a class to all your sidebar widgets then hide them using the appropriate media queries.
http://wordpress.org/plugins/simple-css-for-widgets/
So you would have something like this:
.my-sidebar-widgets {
display:none;
}Alternately, you could hide the entire sidebar but the above will allow you to display certain widgets if desired.
