How to explain this situation in a few Mandarin phrases? Background/Context

I have been spending a lot of time taking care of my mother-in law recently. Because she is from 台山市 I have been learning some Taishanese. She is 85+ and only eats specific foods. So I spend a bit of time buying extra food at dim sum places. I am not Asian so I am having problems understanding what are some appropriate phrases to explain myself when I am shopping on her behalf.

Question

What is the proper way to explain when one is buying for someone else in this situation? I have used the term ngoi mai (buy to go) but I wonder if someone could give me a couple of more sophisticated alternatives in Mandarin.

I also find some of the folks in the restaurant wonder what is going on. How can I explain that I am buying the food to give to my mother-in-law (ngoi mo) but I want to be able to give explanation in Mandarin. The reason is that sometimes I order quite a bit and I can tell the workers are curious. So I would like advice on a couple of Mandarin phrase that I can use to explain the situation.

I am currently stumbling through an explanation where I use terms like lao yan yuen (old folks home) to describe where my mom-in-law is staying. All of this is fine but I'd prefer to have one or two sentences that describe the situation (in Mandarin). 

Any advice on useful Mandarin phrases would be helpful. In this case, I do not have sentences that need translations but I want native speakers to offer an appropriate Mandarin phrase to explain the concepts above and more specifically those below: Again please note, I do not want to sound weird, so I am hoping to find natural sounding alternate phrases (it doesn't have to match the English exactly just the idea needs to be the same).

(Me)
- Hi, I'd like to order some take out

(or in other cases) 


(staff, tells me) you order so much food?
(Me) I have to order to give to my mother-in-law
(staff, tells me) where is your mother-in-law?
(Me) My mother-in-law stays in the old folks home 
(if other suggested Mandarin phrases might apply, please share)


I doubt the results given by Google Translate:

（ME） 
- 你好，我想订一些冒了出来 

（或在其他情况下） 


（工作人员，告诉我）你订购了这么多菜？ 
（我）我要为了给我的母亲在法律 
（工作人员，告诉我）这里是你的母亲，岳母？ 
（我）我妈妈婆婆留在养老院 
（如果其他建议普通话短语可能适用，请分享）
(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.