prepositions - I left them (at) home

Consider this question:

Where are they (things or people)?

Would the following answer be with (at), without it or either one?

I left them (at) home

I have done a quick Google search and found quotes for both cases, with and without:

This Widow's 4 Kids Were Taken After She Left Them Home Alone.

Leaving Your Child Home Alone - KidsHealth

Gerry said, "I left them at home." Gerry sat down and turned on the TV set just as Mark would have done.

I read about "home" being an adverb but also know "stay at home moms" for example. So you see I need definite answers.

Answer

If the choice is between

I left them at home

and

I left them home

I would always choose at home.

at home, along with such other phrases as at work and at school, are fixed and extremely common. So common that I would not depart from them. I would also never say I left them work or ...school.

Yes, home can be an adverb, but I would use this mainly to answer the question

Where are you going?

(I'm going) home.

As far as home alone, this expression is fine, in either

He left the kids at home alone.

He left the kids home alone.

But my feeling is that the use of the latter phrase remains popular in some respects because of the popular movie of the same name: Home Alone, and its sequels.