I still haven't had time to check through the Google link sent by Buteman but have since Google'd using a variety of keywords and not come up with any keyboard shortcut for this model of notebook.
However, I eventually got through to Acer Techies and I was told there was no such keystroke. I'm still not convinced as one of my kittens managed to achieve EXACTLY what I wanted so there must actually be a combination but no-one knows it!!! ;)
@northumbria61 - yes, I do take your point ;)
Keyboard locker - robinofloxley
Pitbull screensaver? - Took me a while ;) but umm, thinking on that ...
@buteman - I checked through this and couldn't find anything that locked the keyboard
@Taff - I didn't know about that; have changed closing to 'do nothing' as that will be useful but still can't read the screen while the keyboard is locked! I do appreciate your 'being in the same shoes', though
@audeal - Although it's not quite what I had in mind, I do like it. I thought maybe using robinofloxley's suggestion (timed yesterday 9.36pm) seeing as I have now worked out what he meant - love it!!! With slide show and appropriate matching sounds might stop 'em for good!!! He! He! Actually, I think my friend could use the toddler key program!!!
So, having had all this variety of suggestions, until I (maybe) happen to discover the keystrokes, I will download Keyboard locker, as suggested by robinofloxley, and see how that works.
As I said, I have done what Taff suggested and can just close the lid if necessary. So, I will have two options.
Thank you, all, for all your help and suggestions. I have appreciated it all, and certainly the humour this thread has contained.