Hi Steve,
Is Unity running smoothly on your grandkids’ PC? Test that first, please. If it is not running smoothly, developing games will not be fun. To test Unity, download one of the course projects from GitHub via the link in the Resources of the last lecture of a section. I don’t know in which course you are enrolled but for the Unity 3D course, I’d suggest to test Zombie Runner and Argon Assault, and for the Unity 3D course Glitch Garden and Tile Vania. If these games are running smoothly in Unity, there is nothing to worry about.
If Unity is a bit laggy, you could set a low quality in Unity and disable “Auto-generate Lighting”. You can find information on this on the internet, maybe also an instruction of what else you could do to make Unity run on slower PCs.
If nothing helps, you could try to work with an outdated version of Unity, maybe Unity 4. However, we do not support that version, so it might be that you’ll have to look for alternative solutions on the internet if something does not work as seen in the videos. Many concepts are still the same, though, so learning the basics of game development with Unity 4 is certainly not a waste of time.
Please feel free to ask our community of students for further advice over on our Discord chat server.
Hopefully, this helped a bit. 
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- Forum User Guides : How to mark a topic as solved