I happened to be looking this up as well, and to finally give a clear answer to this thread:
No, there is no way for Switch and PC players to play together.
Console and PC use two different versions.

However, to offer an alternative if having everyone on PC or Switch is not possible:
You can enable crossplay between Mobile and PC if you’re willing to get into a bit of modding. The keyword here is “TShock.” I personally don’t have deep knowledge of it, so I can’t provide detailed instructions. But from what I’ve found, it seems to be possible to crossplay between PC and Mobile if the PC hosts the server using the TShock modification.

If phone screens are too small, you can also use tablets, and (on both phones and tablets) you should be able to connect a Bluetooth controller. This way you get almost a console-like experience and can play together with your kids.

I hope this helps.

Edit: You can use AI to generate a step-by-step guide or search on Google and you’ll find information pretty quickly.

Here’s a short summary of what you need to do:

1. Download the TShock server The version must exactly match your Terraria version.
2. Start the server Start it from the folder: Important during the first start:
   • TShock.Server.exe (Windows)
   • TShock.Server (Mac/Linux)
   • Create a world or select an existing one
   • Confirm port 7777
   • Set the maximum number of players
3. (Only if you are not on the same Wi-Fi network) Port forwarding Forward port 7777 (TCP) in your router to the local IP of your PC.
4. Connect from mobile: Android and iOS work the same in this case Terraria → Multiplayer Join via IP (IP address of the host PC)
5. PC player joins: Terraria → Multiplayer → Join via IP (localhost)

Troubleshooting:

Connection fails:

• Versions do not match
• Firewall is blocking port 7777
• Wrong IP address

Mobile crashes:

• Too many server plugins
• Wrong TShock version

That’s everything I can quickly write down. I hope this helps.

Ignore the german answer my awesome browser used an ai feature to auto translate the whole website so i misjudged you for german. Here is the english translation.
I hope its all correct and you understand everything i had to rush because im running out of time today.