The answer to this depends on a number of factors, namely the other events you choose to run in Valaki. Consider the characters of the Burgomaster and Izek, Lady Fiona Wachter and her book club, and Rictavio, all in relation to both the party and each other.
Valaki has a lot of potential plot threads going on at once, and was a location my party spent literally months (real time, days in game) of sessions in. They seemed really against the idea of becoming involved in the squabbles of Fiona and the Burgomaster, but I made it clear to the party the longer they stayed in town and did not act the more this situation would fester and tensions would rise. My players kept being under the impression there were spies of Strhad everywhere, so I played into that. I set it up so that the night of the Festival of the Blazing Sun was a culmination of all the events in town, the Feast of St. Andrals, the festival (Fiona tried to pull a coup and kill the burger master with her cultists, the Burgomaster had a funeral for his son (this WAS the festival for my game, it became tentatively named the "Festival of the Burning Son", and the wicker basket his pyre), AND Rictavio's tiger escaped. It took a lot of setup, but it was a hell of a payoff.
The party for their part, prevented the vampire attack, as they decided to stake 4 of the vampires when they retrieved the bones, and slay the other two during the day, I allowed it and basically gave them attack rolls with the stakes (the cleric missed and they had to slay a 3rd spawn). Had they not done so, I would have had them attack the church, possibly even help out in Fiona's coup (I made her a straight up political puppet for Strahd's amusement).
If any of that helps, great. The key is to realize that all of the events in the book need not be run 100% independent of each other or as written. Tweak them around to fit your party and the cards they drew. Another random example? I made Izek's obsession with Ireena instead about one my players, who was a tiefling. I made her his long lost sister, an idea I may have pilfered from the Dice, Camera, Action. It made that character tied into barovia better and was much more interesting.
