No one in my family can speak Spanish but we’ve been trying for more than ten years to learn to converse. Our efforts have gone in waves of high effort and burn out but we are now at a good place where my kids actually want to go on immersion trips to learn to speak Spanish.
They weren’t always so enthusiastic about learning, however. And their lack of effort resulted in very little retention. Still, I don’t consider the lessons they took to be a total loss; the two youngest kids can roll their “r’s.”
It’s been my experience that learning a language when you don’t speak it yourself requires stealthiness. You need to keep the kids exposed more than just weekly tutoring sessions and it has to be fun or they will resist.