just to give you a solid idea here, i did a quick scan of my game's taken list. there are 110 canons listed (109 when you cut the OC section). i have passing familiarity, outside RP, with about 66 of them. there were only 12 that i couldn't think of anything in the canon that could fall under topics too dark or triggering for this game, based on what you've said so far. this is also acknowledging that a lot of them i haven't actually seen and they could have dark stuff i'm not aware of (since i only counted things i knew for sure had dark stuff). that's more than 80% of canons.

it's possible, if extremely unlikely, that every canon i didn't know has no dark stuff, and it's certainly possible my game leans heavily toward darker canons. this is not a scientific number by any means. but i hope this impresses upon you that you're certainly cutting out a very big chunk, if any of the people playing with these canons want to engage with their content.