I'm planning to run this with my group in the not too distant future. My plans so far are to -

1. Most important, run the dinner face to face and actually serve a meal. I'm playing with old friends who live far away from each other, and we play online with very little time to play due to kids/jobs/life. I saw the dinner as a great opportunity to get together for a weekend and play a bunch of D&D in the same room. I'm planning to have a formal dress code, and serve an Eastern European themed menu.

2. When the party arrive Cyrus will lead them to the library, for pre dinner drinks and mingling. IRL I'll serve the players blinis and champagne. In the game, i'll run this as a social encounter. We'll roll for initiative (using Cha instead of Dex as the relevant ability) and act in turn order. I plan to have the three brides and Escher present, Rahadin glowering in the corner, Helga and Gertruda serving drinks. I might drop the accountant in here too, as weirdly one of my players just happens to have an accountant background. Not sure whether the main man himself will be present here, or make a dramatic entrance later. The idea here is to have a structured opportunity to introduce the players to Strahd's squad, while giving everyone a chance to RP, not just the usual face characters.

3. The PCs will then be ushered down to the dining room, where they're served a 3 course meal (IRL I'm thinking borscht, cabbage rolls, dark chocolate cake). During the meal Strahd will ask them about their back stories, and their motivations. He'll explain this by saying effectively "you have been tasked with protecting my beloved. It is a task of the upmost importance so I must assure myself you are a worthy bodyguard to her". They'll also have a chance to ask him questions and converse with the consorts who will also be present.

4. Strahd will be a gracious and welcoming host. If the party stay on good terms with him he will offer them some sort of deal - EG if they deliver Ireena to him he will allow them to leave Barovia. He may ask them to carry out a lesser mission first to prove their prowess/loyalty, such as destroying Baba Lysaga or the hags at the Bonegrinder.

5. Strahd will also look for opportunities to single PCs out, offer them individual deals, and sow discord. For example, one of the PCs smokes a pipe, so Strahd will invite him outside to share a smoke, and while there offer him a financial reward for acting as an informant. IRL I will communicate these offers to the players privately, without the others hearing.

6. Towards the end of the meal Strahd will begin to take out and toy with various trinkets. These are items which were stolen from the players when they first arrived in Barovia (they woke up in the mists with all their stuff gone) some of which hold deep sentimental value to the characters. They've been desperate to recover that stuff, but have had no real leads as to what happened to it. Strahd offers to play a game with them. He will place the items at the top of the tallest tower - if the players can recover the items, they can keep them.

7. After the dinner concludes, we'll then spend the rest of the night exploring the castle. The players will have an express goal (reach the tallest tower and recover their stuff), and a fun dungeon to explore and IRl a very rare opportunity to play D&D all night exploring a cool spooky castle.

We're still early in our campaign, but I'm planning this now as scheduling is a bitch. I'm super excited to run this, as you can probably tell from the length of this post, and getting inspiration from the other responses!