What a horrible experience to go through!
I don't think there's anything cruel with getting a dog for security purposes. After all, many breeds were created specifically for guard dogs!
But there are other considerations. I don't mean to misinterpret or talk down to you, but your original post sounds like you just want a dog for security. You also need to be willing to make the dog a well-loved part of the family, not just a burglar deterrant. Dogs need that kind of support, especially protection breeds. Otherwise, they can develop severe aggression issues, even towards their owners. The dog must also be housed indoors with the rest of the family; if they don't feel the house is "theirs", they may not feel inclined to protect it.
Also, most guardian breeds don't get their protective instincts until they're 1-2 years old. It will be a long time before that puppy will start actually being protective.
I noticed that you've mentioned that you've never had a dog before. That could be a problem. Guardian breeds almost always require an experienced owner; they can be dominant, challenging at times and absolutely need good training. You cannot have a dog of that size and power and leave it untrained. Especially not with small children around.
These dogs also need intense socialization. Meaning that they need to be exposed to all kinds of situations and people when they're puppies. You need to take the pup to the park, the school, have people visit, etc. By being socialized, the puppy learns how to behave in normal, everyday settings. The puppy also learns to distinguish between a normal situation and a bad situation--essential for a guardian dog. You don't want the dog attacking when your children's friends come over.
You also need to get your dog from a good breeder...not a newspaper ad or a pet store. If you get a dog from a bad breeder, you could end up with a lot of health and temperament issues...both are disastrous in a guardian dog. Expect to pay a *lot* of money for a quality pup: $1,000-$2000, depending on the breed. Maybe even more.
These were only a few things you need to consider. I strongly consider getting some good books on raising dogs, and look up some information on guardian breeds. Call some good breeders and ask for information; most of them are more than willing to talk about their dogs. Puppies are a lot of work to raise, almost exactly like a human baby. Be sure you know what you're getting into before you take the plunge.