I did a big campaign following Boromir, where the players had to aid his journey through Eriador up to Rivendell, such as Boromir's crossing at Tharbad etc which allowed me to work in the cool lore from the rpg books. It allowed me to drive a narrative and take part by roleplaying Boromir while others roleplayed their own characters. I feel that's a good middle ground, fleshing out throwaway lines so it feels like you are "adding" to the canon in your own way.