I suspect that, all told, it's about an eight hour task (for two adults and one child), much of it sorting out trash (mostly paper trash and broken toys), baby stuff they've outgrown to donate, and putting the various remaining toys in the right places (toy food with the toy kitchen, little furniture with the dollhouse, tools with the tool bench, etc). Will it all be chaos again at the next party? Maybe. But I have a tentative plan to actually have them clean up the playroom every Sunday at least from now on, and maybe that will mean it will never get to quite this level of disaster again. Crossing all my fingers and toes.
On the plus side, Kavya is delightedly playing with her dollhouse now, for the first time in months, because all the little people and furniture have finally found their way back to it. :-)