Well the mayor is fully aware. She has all of her memories and knows what is going on completely i think. Also Henry was only gone for like half a day and the mayor is not hazy or forgetful about anything so she wouldn’t forget. And i think that they just didn’t notice that Ashley was pregnant for 28 years. It is like they did not age and didn’t notice. They are not aware of the passage of time in any normal way.
And i think Henry is aware completely and did notice. He told Emma that no one can remember their pasts, but Henry isn’t going to know everyone and he is just a kid so he isn’t going to be aware or know a lot of adults. I am surprised that they haven’t talked about his school experience with different students in his class every year because Henry would be the only one aging and all the other kids would be stuck in the same year, but he might just not have any proof. Like there might not be photos and such. And there is a lot of fake information out there like the files about Hansel and Gretel and the pictures of David with Kathryn so it is difficult.
And it is such an insane thing to believe i completely understand why Emma doesn’t. But i do think that it is just that the characters didn’t age for 28 years and just didn’t notice. Henry aged and noticed though and the Queen has her memories, but didn’t age.