Hey ChrisFagan! This is definitely possible but be warned that Multiplayer games are quite a bit more work. You can easily double your workload and headaches as a long more variables come into play. Doubled again if you're going for multiple platforms.
With the https://www.scirra.com/manual/174/multiplayer plugin, you can setup the clients to connect to each other. Given your scenario, you can setup a layout with multiple layers: One layer that will hide everything in the level, a Second layer where all the level information is shown. Then with your clients, if you are Player 1, you hide the information layer and show the hidden layer. Then with Player 2, you can do the opposite and hide the hidden layer and show the information layer. Showing and hiding layers can achieve your effect based on what player you are.
You don't actually have to be in the same layout on each client when using the Multiplayer plugin as long as you don't do any of the automatic movement syncing. Using the messaging system is probably good for your example.
With a single project, you would have to let one client choose to be the host but then have the tablet just choose "JOIN GAME" or something like that and you could direct it to a different layout based on it's platform.
In regards of the cross platform, this is very well suited for that. One client could be on a computer (NWjs) and the other on a tablet(android/iOS).
That is a very quick example but it's definitely possibly. This is a huge topic though so it's hard to give concrete examples.