I didn't like this at all as I felt there were too many things wrong with it that didn't fit with the Harry Potter books. These are a couple of my issues.
Firstly, If at this point Snape had indeed turned spy for Dumbledore, secrecy is vital and he would NOT have hinted to his arch enemy James Potter that he was doing dangerous work to keep him and Lily safe. If word of his spying got back to Voldemort Snape would be dead, and Dumbledore already knew that there was a spy in the Order. Snape and Dumbledore would have kept that between themselves. I doubt Snape would have been following Lily all over the place is such an obvious manner or referring to her as Evans.
In the prisoner of Azkaban, Sirius admits that he and James chose to secretly change from Sirius to Wormtail as Secret Keeper because they suspected Remus of being the spy. In this book it indicates that Wormtail has been approached for the task already, so Remus must already be a suspect. So would you really let him babysit Harry while you go shopping? And would Sirius have gone for a run leaving the suspected traitor with Harry and only Wormtail for protection? Doubtful.
The scene where the Death Eaters catch Wormtail is highly unlikely. I think if Voldemort wanted to get him on side, he wouldn't be grabbing him with his friends so close by in animal form and able to sniff out their known enemies.
It also looks as if events aren't in the right timeline. If they know about the prophecy should they not already be in hiding instead of shopping in Diagon Alley where any wizard can see them? It says they are living in Godric's Hollow yet no Secret Keeper has yet been put into place so they can't be hiding yet. So does that mean Dumbledore lets them live there for a while then tells them to pick a Secret Keeper and then hide in Godric's Hollow again? If they are meant to be hiding they're not doing a very good job of it with Remus the alleged spy in their house, them out shopping and Snape able to follow them!
It was also billed as Harry's first Christmas yet we barely see him in it!
There are just too many plot holes here for me to have enjoyed this read. I get that this is fan fiction but it needs to fit in with the characters that JK Rowling wrote and I don't believe it delivers on that score.