> it's really hard for me to use someone elses computer

How often do you type on someone else's computer? It is not comparable to the amount of time you use your own keyboard.

For the OPs context (their kids) I expect they'll have a lot of typing too do on school computers

I get used to it pretty fast. My keyboard at work in QWERTZ and my keyboard at home is QWERTY. For me, it's a mind thing.

I use QUERTY and UK/US keyboard layout, and the just memorised the Option key combos for the åäö etc. was less hassle for me.

Under linux I do the same, but under windows I have to constantly switch the layout to german, type ä, ö, ü or ß and switch back to english.

That's not the problem though; the annoying thing is when a PC is configured to only have the German layout available, so I constantly mix up Z and Y

This situation got me. Maybe I was rather tired when I did this. It was when one of the letters in my bank's password is a Z but I keep hitting the Y key. After 3 attempts, I got locked out and had to wait until the Monday to contact the bank!

Or you could memorise the ascii codes and type e.g. alt+[keypad] 0248 => ø.

Edit: Is that what GP Bjelkeman meant by "option key combos"?

On macos you can press <Option-u> followed by a vowel and you will get the corresponding Umlaut. (üäö) Additionally there are other combinations for accents and stuff like that.

Thanks, that's good to know!