As usual I am appalled at how often misinformation is shared so blatantly on this site!
First of all, it is NEVER a good idea to paint ANY breed with a rainbow brush, making them all perfect and friendly with no issues to ever worry about.
The simple reality is that while Great Danes DO have a reputation for being "gentle giants", they do indeed retain their guardian instincts, they are and SHOULD be protective and watchful of their home and family, and many in fact CAN be aggressive if not properly bred, trained and socialized. To say that they are all big teddy bears and never have any issues is not only naive, it is setting people up for a big shock when they end up with a dog who has a temperament the person was in no way prepared for.
They are NOT all born gentle. They must be TAUGHT to be gentle. They do not ALL love other animals. Many Great Danes can have high prey drives, can be dog aggressive, same sex aggressive, and MANY more are extremely close to their immediate families, but not huge lovers of every other person on the planet. Which, is not a fault. These dogs are in the mastiff family. They are SUPPOSED to be aloof with strangers. They're not supposed to be like golden retrievers or labs, who want to love on and be friends with every Tom, Dick and Harry they ever meet. They bond intensely with their immediate family, and unless socialized extensively from day one, can become quite territorial of their home and family and over protective if allowed.
If not bred properly....many danes have fear issues. (Unlike those Great Dane owners who will come here and brag about how their dane is terrified of it's own shadow and think it's adorable, I am honest enough to tell you that fear of that sort is NOT a good thing, it is a real fault, as Great Danes are supposed to be brave, not scared of the world! The fact that so many are being bred willy nilly has led to so many danes with iffy temperaments it's not funny.)) Not to mention the health issues that abound if they do not come from parents/bloodlines that have been pre-screened for health issues.
Something for you personally to consider: Many reputable rescues and breeders simply refuse to adopt or sell a pup to a family with young children. Not because the breed is horrible with children, but because all too often we see them being dumped/rehomed at six months or so, when the kids have been knocked around, and accidentally injured one too many times. It's almost always the dog who suffers when this happens, and as such breeders do not want to see their pups being in homes with small children. Of course you won't have any problem at all finding a BYB to hand over a pup, no matter your lifestyle, financial situation or experience, as long as you have a fist full of cash to pay them with. But you are taking a HUGE risk by buying that pup from that type of breeder. Temperament and health is a crap shoot with those breeders.
Many say that if you do have kids and get a dane, that females tend to be more patient and gentle with them. I prefer males of any breed/species so I can't tell you from experience, just that the majority of people I know would say a female is more tolerant, more attentive and patient with kids.
No one here can guarantee that the dane you end up with will be a big loveable goofball. That's going to depend on genetic temperament, aka proper breeding of dogs that are mentally and physically stable, as well as training and socialization from day one.
I suggest you join Danes online forum...there are literally thousands of owners, breeders and those rescuers, who have experience with every type of temperament, health issue,etc and by reading through the threads, you will get a much clearer idea of what living with a GD is REALLY like. Yahoo answers is NOT the place to find real and helpful info on this breed. Trust me, I hear more misinformation on here from supposed GD owners and experienced dog people than I hear truth.
There truly is nothing in this world like sharing your life with a Great Dane, but they are not for everyone, they are not always easy, and you should always do a LOT of research and honest questioning of yourself before going into dane ownership for the first time. Best of luck to you, whatever you decide.