Right, looked up the Annotated, and it starts with Anu and Padomay already present, which means that already, Anu cannot be the Godhead.
As we see, the two brothers just 'appeared'. There really isn't all that much, but from what I take it, it more about the two suddenly came to being when the Godhead's mind split in two, and the brothers, Anu and Padomay, were born.
For me, I see it less as him dreaming up everything, because Nir already created Creation, and instead went to to Aetherius and took a depression nap and didn't come back until Padomay returned after nursing his injuries from before.
Though, I personally do not find both Children's and Annotated to be literal, but a metaphorical view of the creation of the world so that mortals have an easier time understanding all the hubbub.