Sara is still quite a young name here - I grew up with a lot of Sara/Sarahs and they are now having their own kids, so using
Sara would be akin to naming a baby
Jennifer or
Jessica. Yes, they would probably be the only on in their class, but they might share their name with half their classmate's mothers! :)
It's also indistinguishable from
Sarah here, in terms of pronunciation. The only thing that sets it apart is that is looks a bit more modern, maybe? It has a very youthful vibe to it.
Sarah is more homey and cozy and hunkered-down sensible classic.
Sara is a bit dated to the 80's and 90's, but it has a breezy energetic charm.