I think it’s ok. Maybe not the way I would put things, I would probably say instead :

Il se trouve que Chloé at Sarah ont toutes les deux trente ans.

Yes, this kind of incise is common, especially in spoken French, with coïncidence and other terms like surprise.

It is a shortened version of quelle coïncidence !, quelle surprise !, and is often used ironically.

A similar interjection can be “tada !” (reproducing the sound of a drum roll).

Due to its mainly oral usage, it is difficult to find occurrences of coïncidence used that way but here is a similar usage:

Sur la base d’un vote de 129 entraîneurs, c’est – quelle surprise ! – le Français Zinedine Zidane qui a été couronné.
Le Point, 1998