Here is a website with some ideas for lesson plans on King Arthur. If you are using Ambleside Online, these ideas would go well with Years 5 or 7. I would simplify some things if using the questions/activities for Year 5.
For instance, Mariel just finished reading Pyle's King Arthur. I haven't required her to formally narrate throughout the book, but now that she has finished it, I have given her an exam-type question that I adapted from this website:
Original Question: What are the fundamentals of chivalry as portrayed through the Arthurian Legends, and why was this a relevant social issue during the early middle ages?
Mariel's Question: What makes a knight chivalrous? Give examples.
(I ought to have been able to come up with that question without the help of a website, but sometimes my mind goes blank.)