I don’t think August as Peter Pan makes much sense at all. First off- we have seen no references to any of the Pan characters or stories. I don’t think Pan would even be from Fairytale land itself anyway. Wendy, Michael, and John were from a very specific time and place in our world, and Neverland is like Wonderland- a completely different realm. Not to say we won’t see his story in future episodes, but I think having August turn out to be him would be completely random and out of place.
Pinocchio on the other hand- he was already human when the curse was enacted, so he would be human in Storybrooke and our world. They made a point to tell us way back in Archie’s backstory that Gepetto’s Storybrooke alter ego had no children. Originally, I thought that was just the curse taking away his happily ever after, but now I think it’s because Pinocchio somehow escaped through the wardrobe. Gepetto helped build the wardrobe- perhaps he hid his son there. The newspaper article about Emma as a baby said she was found by a 7 year old boy.
Plus, August knows all about the book (he may have written it) and who Emma is….he has to be an insider. If Pinocchio came to our world at age 7 and grew up, he’d still remember everything. The only people who knew about Emma being the savior were those who worked closely with the royal couple.
As far as August being Rumple’s son, the writers have indicated that Rumple became the Dark One centuries before the curse was enacted, so the only way this would be remotely plausible would be if Bae was somehow stuck frozen in time for many years.