I am excited!
I found one reference, for the small write up I had given about Golu having made it's beginning during the reign of the Vijaynagar Kings (Krishnadevaraya).
There is one paragraph in between if you have the patience to read. The 4th para to be precise. It tells that this custom started during the Vijaynagar period, and there is a reference to Golu dolls in Saraswathi Mahal Library ( Tanjavur)
Yipee...I feel happy to have found it.
Yet I know I read a longer bit somewhere else...I am still searching for this...