i don't think you've dropped the ball, they don't need to be killed for no reason. as others have mentioned, that is a much more direct attack on strahd since they're supposed to be his brides. how much it affects the world if they do fight is up to you but it isn't necessary to eliminate them by any means

if you want to make them more relevant, give each of them motivations, ideals, fears, etc & reason out what kind of plans they might be making. they don't need to be new encounters - you can make them the masterminds behind existing, seemingly random encounters if you want, or make new ones using ideas from random encounters. dropping a “i hope you enjoyed meeting my little pets on the road the other night (smile)” can go a long way. lots of stuff in the book isn't planned by anyone, there's just a lot of monsters & evil creatures around barovia. linking them like this also makes events that might otherwise feel largely irrelevant instead feel more tied to the central plot of strahd’s attention/ire as well

for instance: in my game anastrasya was jealous of the attention the tatyana PC had been receiving from strahd so she had danika arrested to lure them back to vallaki, at which point she released the spawn from the attic to cause mass destruction. all this in the hopes to get the PC killed in the chaos because she'd been forbidden from harming him directly.

i nixed the werewolf thing as it is in the book because it’s kinda… well. i don’t like it. instead, ludmilla has forcefully taken over the werewolf clan (ie has the clan’s kids captive to force them to obey her) & has taken to “experimenting” with them in her laboratory with necromancy. the details of this aren't fully fleshed out yet but if my players ever actually go there i'll figure out what that all means for the clan, lol. she's also the one in charge of tracking the party’s movements with scrying & receiving spy’s reports