I'll try and retell the story in a way to me that makes sense, but without giving out specific details. So, beware, this is laden full of spoilers.
In the beginning the theme appears it might appeal to Harry Potter fans -- and I am not a Harry Potter fan. A particular character captures my attention, and ought to capture the attention of the audience. This character, our prime protagonist, Rudolph draws attention because his social behavior differs from the rest; radical individualism I suppose?
We learn that he is trying to break free from tradition; a tradition set for him to keep him safe. He wants change. He wants to grow. His older brother Gregory taking that charge of change, Rudolph is left to witness the price of breaking free from tradition, and soon the entire clan is unsafe; a certainly unfamiliar situation.
In order for Rudolph to get used to the unfamiliar situation he meets a boy Tony Thompson, a vampire enthusiast by accident. Rudolph also spends a lot of time flying outside, something his father has forbidden him to do. Although the difference between him flying then outside for fun, and his role in flying in the movie has its purpose to help the story move on. Rudolph also spends more time enlightening his family, kind of like the philosopher of the Plato's cave allegory.
Rudolph may have not seen it, but he learns a lot from Tony Thompson, and thereby help Rudolph achieve growth he earlier wanted. He learns stuff like "cool" and "sick", words which Rudolph at first takes too literally. Meanwhile, Tony Thompson's parents makes comments throughout the movie how Tony Thompson is growing and being mature. The friendship of Tony and Rudolph stimulates their own respective growths.
Rudolph may have gained so much growth, but in the process, he lost his home. It's a historic home of 300 years or more, thus the lost of it could be in human terms mean the destruction of heritage sites. Contrast the historic home being destroyed in seconds by modern technology.
With the help of Tony however, Rudolph and the clan were able to revitalize vamparism by taking over a Castle-Inn. To me, this is rather sad, because the couple who owns the Castle-Inn appear to be honest Christians. The owners however rarely have guests, so it made sense to Tony for the vampires to occupy it completely. Caveat for the vampires however is that the Castle-Inn has too much garlic.
With the vampirism revitalized by taking the Castle-Inn, the only difference with this sort of vamparism is that no humans shall be victimized; sucking blood from livestock (cows) suffice.
The film thematically presents cultures (Romanian Transylvanian and German culture) and its interaction to technologies (Maney's technological ingenuity being used and abused by Rookery's zeal to destroy Vampires which bordered on unethical; if it meant killing a human child to stop Vampires, Rookery would do so).
There also seems to be some sort of Romeo (humans) and Juliette (vampires) misunderstanding between humans and vampires. Rookery, hotel owners, and Tony's parents don't perceive vampires too well, except for Tony Thompson himself. The entire vampire clan maybe mainly Rudolph's dad and mom, don't like "mortals". Rudolph initially didn't trust mortals neither. The German uncles of Rudolph however were more friendly to mortals, having waved at Tony in the beginning.
The movie is funny. Lost in translation situations between Rudolph and Tony are funny. Maney and Rookery interactions are funny. Rookery trying in vain to capture but only to get defeated is funny (i.e. when Tony switched the alligator clips for a circuit, to destroy the source).