How to make image menu items responsive as a combined group in twenty-eleven

Hello
Can anyone please help?
I am using a twenty-eleven child theme for a static website (www.notquitenormal.net) using images as menu items rather than the default text and there are up to five images on any page menu.
My problem is, although the theme is responsive and adjusts individual images according to the size of the user device, I want my website to adjust the combined image group (including borders, paddings, and margins) but still keep each image individually clickable as a separate menu item.
Is there a way I can do this?
If there is, please let me know (and make it as simple and as idiot-proof as possible because my level of competence is beginner!)
Many thanks
GL