After sharing what little food they had, the couple let the angels sleep in their bed.

是的，感叹句完全可以作宾语。你的句子中，what little food they had 便是一例。又如：

“她认识到她是多么傻啊。”

She realized what a fool she was.

She realized how foolish she was.

再举几个跟你的例句类似的句子：

His mother sent him what little money she had saved.  他的母亲把所有仅存的钱都寄给他了。

She was robbed of what little money she had.  她仅有的一点儿钱都被抢了。

I told him what little I knew on the subject.  我把我对这个问题仅知道的一点都告诉了他。