Sorry, Guru, but I can't find an easy way to take a screenshot on the phone and then save it to Drive and thence to my PC to send to you. The checkbox button appears on the toolbar in Evernote for Android, in the line of icons, just to the right of Bold, Italic and Underline. It does work, in that it places an empty checkbox into the text. But you cannot do anything with that checkbox, and you can't 'tick' it (e.g. by typing a space, as on a PC). As far as I can tell, it is simply a checkbox symbol character with no functionality. I would be happy with that if there were a simpler way of inserting a ticked checkbox.
The App is version 8.3 and I am running Android 7.0.