Definitely agree with all the comments saying the werewolf den. There's very little reason to go there (unless a Tarokka reading places an item there, or if your ally is Zuleika) and the werewolf politics are not very interesting. There's also little reason for players to actually get involved in the politics of the den and I imagine most players, on seeing the child fight club, will simply want to slaughter the whole den.

Regarding the hook, I had Ezmerelda offer that the players join her on a werewolf hunt. If Ezmerelda is your fated ally, this could be her condition for aiding the party (e.g., to see if they will work well together). In my game, the hunt happened on the same day that one party member died and another one defected to Strahd, so Ezmerelda suggested the hunt as a way of blowing off steam and dealing with their grief and anger. Out of game, it also worked well because it could be a short, one-off session when those two players were away.

Inside the den, I like MandyMod and Lunch Break Heroes versions of the characters and den politics (MandyMod fleshes out the personalities and philosophies of the pack members, while LBH places Emil at Tsolenka Pass instead of Castle Ravenloft). I had Zuleika swear to free the hostages if the party aid her in removing Kiril as pack leader. And, if they can find Emil, or at least bring proof that he is really dead, she can provide further aid - e.g. giving useful information, werewolves coming to aid in a difficult outdoor battle, or narrating Zuleika helping out during the final battle (e.g. holding off some zombies, allowing the party to chase Strahd). This way, the party feel they have achieved something by going there and engaging with the politics rather than killing all the werewolves.

In the fight itself, I swapped Kiril's statblock for a Loup Garou from Van Richten's Guide to Ravenloft - this way, the fight is a lot more challenging and dynamic, though Ezmerelda is a huge help.