I love this challenge!
What adorable little children.
I also think the bear's pads on it's 'arms' are different from in the photo - longer, maybe mended, and extended to cover damage?
As I am coming to this late in the piece, I think the older child is Dora, and the younger child is Glyn, and Glyn is 1 year and 5 months old. Phrasing is a bit odd on the back of the postcard but that is my understanding of the wording. Might the tankard be a first birthday present for Glyn, though it could be a christening present I suppose?
There appears to be a picture in the locket around Dora's neck. I thought it may be a picture of Glyn - but am likely to be mistaken.
Lovely image.