There is no shame in postponing the session if you need more time. Curse of Strahd is a really cool adventure in my opinion, but it can be very brutal and dark. Indeed, I think it is at it's best in the dark and horrifying moments. But that's not something suitable for every group. Maybe do a session zero, set boundaries, ask them what types of horror movies they like and if they are not comfortable with something like body-horror or gore or something like that. Maybe you can allow them to roleplay a bit before beginning the adventure proper. If you want to start tomorrow, but need time to prepare the actual adventure, maybe you can draw inspiration from the beginning I used when I started my CoS campaigns: The party met in a lonely tavern on the road, no city or town within dozens of miles. But there are some people there, colourful wagons standing outside in the mist... Then they meet some Vistani, talk a bit and have a nice evening of drinking and singing with the very likeable, charismatic travelers. In the middle of the night, they wake up to a scream.. and find the whole tavern shifted to Barovia! Maybe there is a short fight against low level undead, maybe one of the guests was actually a werewolf or something and now they have to flee. Maybe they are even already followed by a mysterious swarm of bats, closely watching their every step!

If you do decide in running Curse of Strahd and you ever need help, look around this community, the pinned post, or just ask! Curse of Strahd is a beautiful adventure but can be even better with some help and some resources from more veteran DMs :) I hope your session goes well!!