That's a perfectly cromulent way to set it up, but just to offer an alternative, if you have a group of players that are likely to buy in, you can involve them early in the process.
In this case the goal isn't to scare them or otherwise go for direct emotional impact; it's to bring them into the storytelling process to create a mood. If it works, the players create characters that are very well suited for the campaign, but not in the sense that they're vampire hunters and such. Rather, they deliberately create characters with vulnerable backgrounds and crippling emotional stakes. Jonathan Harker, for example, begins his story engaged, and why not? He's young, he's moving up in life, and he doesn't suspect any danger in his job. This would be an unusual starting point for a D&D PC; having a noncombatant fiancee with a very real chance of him/her being targeted and killed. It's not something you'd do even in a conventional D&D campaign. A player would only do something like this if they bought into the "mess with me" element of a horror campaign. Bonds are what send you walking back into the abyss you'd just narrowly escaped.
Skill/combat-wise they'd be above their heads by design, but not quite so helpless as to be bored or frustrated. For example, no character would start out with a family val-u-pak of holy water (makes sense if the cleric has a vial, OK, but not nearly enough), but a character can start out with strong investigation skills, like a typical Lovecraftian protagonist, so they at least have a puncher's chance of finding out what's going on before they're picked off. If someone shows up "coincidentally" with a half-vampire undead-hunting ranger/cleric with an entire garlic harvest, rip the sheet up and tell them to start over. For that matter, you can even start them at "level zero"; after all, Harker wasn't a fighter. Getting dragged into a world of horror becomes the motivation to gain class levels in the first place.
To reiterate, this isn't a "better" way to do it; just an alternative. Depends on the group, YMMV.
