Changing the keys to edit menu entries and showing command line

[Joseba Nevado]

Hello everybody,

I have been searching the web looking for a way to change the default 
keys that you need to press in order to edit menu entries or entering 
command line ('e' and 'c' by default) so they are not easily pressed.
The thing is that I share my PC with my parents, and they know nothing 
about computers (they just boot Windows and play card games xD), and I 
recently had to reinstall GRUB 2 because they actually managed to 
corrupt GRUB somehow (don't ask me how, they said they just pressed "one 
key").
So I'm thinking on changing these default keys and setting them to ALT+e 
and ALT+c for example.
Is there any way to do this? Thank you!

Best regards,
Joseba Nevado.