Ooooo Lu, this is what I do. But I do it in full view and with the outraged screeches of a three year old to accompany me, just to add to the drama. It's amazing hwo quickly toys get tidied up for the next week...!

Alternatively, toys must get tidied before something else (desired) is given over. Snack, TV show, another toy, whatever. That works even better, because the motivation is positive and my voice gets a rest.