How about the two of us taking a walk down the garden?

How about the two of us taking a walk down the garden。这里为何要用doing，假如若是about 后面+名词所以doing动名词，那样the two of us 已经是名词了，为何还要用doing？

这句话的谓语是doing吗，为何么？为何没助动词be？

这句话的主语是two of us。谓语是taking为何是ing形式，宾语是 the garden  如此剖析对吗？？

Howabout the two of us taking a walk down the garden?

由于是用于介词about 后作宾语，所以要用动名词；动名词前面的the two of us 是动名词的逻辑主语。