can my children play multiplayer?

If you have Bedrock on each device, you should be able to natively cross-play between all of them, no need for external software.

At most, you may need to or want to look into setting up a bedrock server to host on LAN, but that’s not even necessary if the one with the computer will be able to host it every time. In Minecraft’s help section for LAN on W10 it should be as simple as someone doing the following steps (after making sure everyone is on the same wifi network:

Start a LAN game

• Click Play.
• Click the pen icon to create a new world or edit a current world.
• Go to Multiplayer and make sure that Visible to LAN Players is enabled.
• Choose Create or Play to start the world.

Join a LAN game

• Go to the Play menu.
• Click the Friends tab and look for available LAN Games.

You should also be able to set up a dedicated bedrock server but that’s a little more complicated. The advantage though is that it doesn’t require the same player to host each time, as it’s a separate instance that anyone can join. And it should natively work on LAN, though finding and connecting is a little more complex as you’ll need to figure out your local IP (you don’t need your global IP unless you’re trying to make it connectable to devices not on your home network).

Yes, it's possible with Floodgate and Geyser.

Geyser is a bridge between Minecraft Bedrock Edition and Minecraft Java Edition, closing the gap for those wanting to play true cross-platform.

Floodgate is a hybrid mode plugin which allows for Minecraft Bedrock accounts to join Minecraft Java Edition servers without needing a Minecraft Java Edition account. This plugin can be installed in addition to Geyser, but, unlike Geyser, Floodgate can only be installed as a plugin on Spigot (including Paper and forks), Bungeecord, and Velocity, and can only be utilized on servers that have it installed.

Geyser is the program that lets you connect Minecraft Bedrock Edition to Minecraft Java server and Floodgate is a plugin that you install onto the Minecraft server to let you use accounts from the Bedrock editions of Minecraft (Android Minecraft versions are Bedrock editions and Minecraft versions on PC are Java editions).

If you have bought Minecraft on all 3 tablets, and on the Windows 10 PC, you are ready to set up everything. Just follow the video guides of Geyser and the text instructions of Floodgate.

Keep in mind that you need to set up everything on a powerful PC. A Windows 10 PC should do the trick, assuming it has more than 4GB of RAM. You need to host a server on a PC, and then that PC and all the tablets need to connect to the server.

Once you have everything ready, the server will appear on the tab "Friends" on the Bedrock editions and on the PC you will need to connect to "localhost".

Useful links:

• These are the text instructions to install and setup a Minecraft Java Edition Server. It is a "Paper" server. This version works great with Floodgate.

• These are the text instructions to install a standalone version of Geyser.

• These are the text instructions to install Floodgate on a server.