Read books by Xiao-Lei Wang
The author whose works are linked here is an education professor and mother of multilinguals.https://www.bilingualism-matters.org/ - This "was established in 2008 at the University of Edinburgh as an information service for parents. In 2014 it became a Research and Information Centre." It is now "a growing community of international language experts engaging the public with the latest research about bilingualism and language learning."
http://talknua.com/ - This is the personal blog of Speech and Language Therapist Mary-Pat O'Malley, of the National University of Ireland. She is also on of the admins of the Facebook group "Becoming Bilingual". Lots of support, tips and resources are freely available via her blog.
This Irish enterprise works "to promote multilingualism and intercultural dialogue [...] through three interconnected goals:
Educating and empowering parents and educators
Creating networks and support groups for multilingual families
Raising awareness of the benefits of multilingualism and intercultural dialogue for individuals and society"
Lots of guidance and resources available here.