Along the lines this thread is already headed...

You could build a false floor in your living room about 18 inches above the real floor. Let your kid have free reign in the subfloor area, and keep your speakers, components, and the rest of your furniture on the raised floor. This you protect your speakers, electronics, furniture, and even your walls from wandering hands, spills, and crayons.

This could also be a solution to austinbirdman's volume knob issues as well.