How to explain this situation in a few Mandarin phrases?
(Me) - Hi, I'd like to order some take out

你好，我想叫一些外卖

(staff, tells me) you order so much food?

你叫了这么多东西啊？

(Me) I have to order to give to my mother-in-law

我帮我岳母叫的。

(staff, tells me) where is your mother-in-law?

你岳母在哪里？

(Me) My mother-in-law stays in the old folks home

我岳母住在养老院

Please be noted that there're different expressions in Mandarin for mother-in-law. If you are male, your mother-in-law is 岳母. A female's mother-in-law is called 婆婆. Because you mentioned you call her ngoi mo, she must be your 岳母 or else she would be called gah po.