I like this approach to describing B-trees! I recently taught B-trees for a data structures course and presented them using a similar method. Thought I'd leave the link in case it was useful: http://web.stanford.edu/class/cs166/lectures/05/Slides05.pdf
Really wonderful presentation, thank you! Especially the way the "animations" (the slides with changes, actually) convey the dynamics in the sequence of events explained.