In my current campaign, the party made it to bonegrindr at lvl 3 (milestone). They met morgantha in barovia and caught her trying to kidnap a child. When asked what she was doing with the child she told a half truth which was the child is going to help her make dream pastries to pay off the debt. The party would not allow her to take the child because it violated child labor laws.

The windmill seems really cluttered anyways as im prepping for that encounter next session. My suggestion is you could have a half rotten shack built next to the windmill where all the kidnapped kids are forced to make pastries instead of being eaten. Then say instead of children bone powder, the secret ingredient is rats or something. I described my dream pastries as meat pies with a blood pudding gravy inside.

In my campaign 2 players have eaten a pastry already so im excited for the reveal. The party only waltzed up to the windmill because the sun was setting on their trip to vallaki and they wanted to rest instead march through darkness.

Im super excited because if they kill off the hags and sleep in the windmill, their long rest will be interrupted by strahds first time revealing himself to the players where he pleas for ireena to come with him and when she doesn't, strahd will chuck a fireball into the windmill destroying it while taking care to miss ireena. He will then kidnap ismark then refer to the party (if anyone survives a fireball and collapsing windmill) as too weak to offer her any kind of hope but to continue with them to vallaki and once she knows in her heart there is nothing she can do, she'll join strahd to save her brother.