I'd recommend a secure point out in the garden somewhere, and a decent padlock and chain. Don't let the little darlings even NEAR your stereo.
Sandwiches in the video, misc fluids in lp sleeves (with the lp!), cassette tape pulled out, jammy fingers on every knob/switch/slider, and that's when keeping them under close supervision!
With hindsight, I'd suggest buying a load of old gear from a jumble sale, leave that just within their reach, but put the real stuff completely out of their reach (and pref in a completely seperate buolding altogether).
Nige