I had a feeling that the 'best' solution would be some kind of belt. It seems a bit strange to me that you can't lock the technics hinges straight. I ordered the no-hinges from KAB, but they are essentially feet which would sill allow them to push around the top.
My hope is that this ends around 3 and a half or so. That means another 18months with the twins and another 3 and a half years for the newborn.
Gadfly...you'd be amazed at how many times I 'work' with my boys to get them to understand that the turntable is off limits. They LOVE to lift the top just a little to see the platter spin and to push the buttons.