Timeline/Historical contextual study: Victorian, WW1, Cold War British lit, Beat Generation, Post 9/11 lit, Slave Narratives, Great Depression, Civil Rights lit, AIDs 1981-5 literature, etc.
You'd look at how the historical period influenced literature from that historical time.
For my diss I did something completely unexpected which was looking at how the literary trope of the "Other" was used in British Cold War literature.
I didn't know anything about British 1950-60s literature, Cold War literature/politics/history, etc.
Also, I studied at Glasgow University and there was a specific course on Children's Literature and I believe other universities do Masters courses on the topic.
I would try and get the reading list for these courses online; that should be about to point you in the right direction.
The literature review has been described as a "report of primary scholarship" (Cooper, 1988) and "an interpretation and synthesis of published work" (Merriam, 1988, quoted by Murray, 2002).
The two key words here are scholarship and synthesis: a literature review relates particular research to the a wider field.
But found it very rewarding learning something new and totally independent on what I had studied before. Not to say you can't do this with children's literature, but this genre of academic study is limited.
When working on a dissertation, it is usually required to read different literature sources.