I would personally suggest that the parents do not speak on the child's behalf, such as ordering meals at restaurants and the like. My parents did this (in good faith, they didn't know any better) and I think it ended up sort of reinforcing my fear of speaking to people, make me feel like I was unable, when in reality I was perfectly able, it just took me a little bit longer than other people. I am aware however that this is probably incredibly dependent on the individual so maybe tread lightly with this one. Also, if/when the child is of proper age to do so, definitely encourage them to socialize and make friends, building social skills is something that I think a lot of people gloss over and it is, in my opinion, exponentially more important than actually achieving fluency.