Aww, jeeze, Have we become so over-protective that we now have to whitewash DISNEY movies for our kids?
Anyway, the main villain is a voodoo priest so we do have some voodoo magic shenanigans. When the "Shadow man" does his magic there is some talking voodoo masks and walking sack dolls (think main characters from ps3 game Little big planet) hop around. The "Shadow man" has some shadow minions he orders around that look menacing. The final battle does take place in a cemetary but I don't think we see anything other then tombstones. That's about it.
There was a rather intense moment where spoilers, The Shadow man steps on a firefly friend, killing him but it wasn't scary so much as intense. "Shadow Man" was a bad person and the firefly gave his life for his friends.
No-one, not even a three year old will get nightmares from this cartoon. If you're an over-protective Christian then you might not want to see this movie because it does feature voodoo magic, but then you'd be an idiot because magic has been a mainstay in Disney films all the way to Snow White and the Witches magic apple.
IMO, kids need to see some age-appropriate scary stuff. Think the wolf from Never-ending Story, he was scary. Think the Gnome King from Return to Ox. Kids LIKE being scared, thats why they enjoy Halloween. Even if "Princess and the Frog" was scary, I'd encourage you to take your kids to see it, but its not.
Anastasia and its zombie antagonist who dances with bugs was more scary then Princess and Frog.