The vampires pack is great, even aside from gameplay. There's some really elegant gothic-type décor and clothing, and the ever-popular Vattore siblings.
As for gameplay though, they've added the ability to turn off vampire visits in game options, so you no longer have to worry about someone breaking in while you're trying to sleep. The game may generate townies who are vampires, but I haven't had any sims turned without my permission.
If you get the werewolves pack, you can also change game settings so that werewolves won't appear in-form outside of Moonwood Mills, unless you're playing them. One last tip, since you're considering a family: Werewolves and vampires have some unique interactions, and the werewolf pack comes with lore for werewolves, vampires, and spellcasters.