A nice idea, for the spouse who doesn't speak the language. In case of WA and Max I once heard she speaks Spanish to the kids and that he was or is also trying to learn the language.
Acquaintances are a German-Polish couple with kids in the Netherlands. They can't speak each other language fluently so they predominantly use English between them. With their kids they each use predominantly their only language. At school and in the neighbourhood the kids pick up Dutch. There parent can also speak sufficiently Dutch.
I once heard the story that dad, to tease mum a bit, told the kids to speak German to mummy (as she couldn't understand it
) on some moments.
Or a former colleague of Israel who tried to pick up a bit of Dutch. But was dumfounded when neighbor kids came to her door. Asking something she didn't understand. Until her young daughter said those kids just wanted to get their ball, which had landed in their garden (duh!?)