One thing your child has heard a lot by now but never had explicitly explained is the phrase "zhe shi shenme?" It literally means " this is what?" and is used when you point to something, like maybe a color, and ask zhe shi shenme? (Remember the shi sounds more like shr)
You can use this to quiz vocabulary. Colors and numbers especially at this point. Point to a seven and ask "zhe shi shenme?" They should be able to tell you in Chinese.
If you want to ask them about family members you can use a similar phrase "zhe (this) shi (is) shei (who)?"
The shei sounds like shay.
A short vocabulary list will be sent home tomorrow, so ask about it and try to help them review these words.