Our narrator sure knows a lot about a lot. In fact, it seems like she knows everything. She can zoom in and out on all the characters, jump from place to place, and even read the thoughts of the main players.
Let's take a look at the first words of each paragraph in the Prologue:
One day at that time, not so very long ago, three things happened and at first there appeared to be no connection between them.
At dawn, Mae Tuck set out on her horse […]
At noontime, Winnie Foster […] lost her patience at last […]
And at sunset a stranger appeared […]
No connection, you would agree. But things can come together in strange ways. (1.2-6)
There are our three main storylines and the narrator knows them all. This makes him omniscient, or all-knowing.
Guess who else is all-knowing? You. Yep, that's right. Think about it. The narrator tells us everything, which means we know more than any of the characters in the book. Think about it. Winnie, the Tucks, and even the toad all go their separate ways, and we're the only ones who get to see it all go down.
How would things be different if Tuck Everlasting were written from Winnie's point of view? What would we miss out on? What would be gain?