If you’re setting up an account that you manage with parental control, create shortcuts and enable apps you want her to use. Enlarging the icons is pretty easy; from the Finder’s View menu, select Show View Options and set the icon size to the biggest there is – you can also adjust the text, or choose to only show icons. It would also be worth setting the ‘Key Repeat Rate’ to slow (Sys Prefs -> Keyboard & Mouse).