Expat family on home language maintenance

In this video our multilingual expat family discusses language use, home language maintenance and explicit language policies in the family.

This family is managing several languages at the same time. Throughout the years they have developed and implemented several explicit family language polices in order to transmit and foster their languages? They have changed language use among themselves or they go through great lengths to buy books in different languages. Can you think of other family language polices that would help multilingual competences to develop?