I'm very happy you got them, they are stunning and appear to be in really good health and so does the chicks!!
I'm far from being an expert on mutations, and the adult male you just got may have opaline on him, I just can't tell for sure. He has a really interesting mix of colours. If he is visually opaline, then it's possible for the pair to have a true rainbow, if the chick gets the visual opaline trait and loses the spangle mutation.
Another gorgeous couple, apart from being opaline the male is also a spangle and both appear to be dominant pieds. If you pair the female dominant pied opaline with the male you just got, then the male chicks would be split for opaline and on the next generation you could get the rainbow chicks.
If the male is really opaline, then you can get visual opalines of both genders and the chicks would have to lose the spangle and dominant pied traits and inherit the yellow face. It would also be necessary for the female to be split for greywing.