Well the statement, "lets eat grandma" was a demonstration of a lack of proper punctuation. The fact that it caused confusion as to it's precise meaning, only illustrates further the point.
It shouldn't be confusing; it's unambiguously equivalent to "Let us put Grandma into our digestive systems." My grandmother didn't eat well, however, so I'll stick to my usual diet.
¡¡dlǝɥ ǝuoǝɯos 'uɐɟ ƃuılıǝɔ ʎɯ ɯoɹɟ ƃuıƃuɐɥ ɯɐ ı