Bliss
Well, they aren't exactly playing together, but almost! At least I know where they both are (especially Liam!) and there is only one mess.
Megan mostly builds and cooks with her Playdough. Liam mostly destroys, ripping a big blog into smaller ones. And there is some purposeful dropping, too. See how half of Liam's Playdough is on the floor in the lower left. There's another blob of Liam's Playdough that you can't see, but that's because he ate it. It is non-toxic, right?