In a perfect world...
Motion sensitive exterior lighting, a good strong security door on all external doors with strong deadbolts and a dog (even little ones) are great security systems. Some will also install an electronic security system as well. Me I don't feel like paying someone else to monitor my home 24/7 so I just put those cool little magnetic alarms on my doors and set them to go off when the door is opened before I go to bed.
Indoors I have night lights set strategically throughout the house - they're cheap and don't cost a lot in electricity if you get the ones that are LED and have a light sensor on them so they turn off in brighter light sources. This isn't because I'm afraid of the dark - but because I have very young children in the house who will get up in the middle of the night to go to the bathroom. Don't want them to trip over something, walk into the counter etc. as they make their way to the bathroom.
This also helps eliminate the dark blob in the dark doorway problem. When I awake in the middle of the night I can see perfectly fine (albeit everything is fuzzy since I need glasses for really good vision) but at least I don't just see a dark blob.
If anyone broke into my home they'd have to contend with my dog - a big female mastiff. She's friendly and all cuddles when during the day and when she's with family but at night she's extremely defensive of the house. I nearly got attacked one night when I came home late after a party with some old friends - I opened the door to a very ferocious looking barking and growling dog that was frothing at the mouth. Of course once she realized it was me she proceeded to wipe the drool off on my pants as she nuzzled against me for attention. My wife was awakened by the noise the dog made and had come to investigate with my 12 ga. in hand.
So in my perfect world first a criminal would have to decide if they want to try to access a well lit home. Second they'd have the security doors to contend with or go through a window. Once they gain access they'd have to contend with a ****** off 180lb mastiff. IF they somehow got past her they'd meet me armed with my pump 12 ga.
Just to be clear I sleep with a loaded 12 ga. next to my bed - 5 rds of 2 3/4" 4 shot in the mag and the chamber clear. I also have a Bersa Ultra Compact 45 under my pillow - 7 in the mag and one in the chamber - decocked. My wife sleeps with her LCP loaded (full mag with one in the chamber) in her night stand. Are we afraid of being broken into? Not particularly. We live in the country and the chances of someone coming to our home to burglarize it or invade it are slim. Are we going to set ourselves up to become victims in case the slim chance becomes reality? Hell no - not with young kids in the house.
Oh and about the kids - my 4 yr old daughter spends time at the range with my wife and I - she shoots her pink Cricket .22LR rifle. She already knows and can recite the 4 basic rules of firearms safety and can knock soda cans off posts at 25 yds with her rifle. My 13 yr old daughter has been shooting with me since she was 4 and because she has better eyesight I think she can actually out shoot me from a bench... My 8 yr old shoots with us - he has his own 10/22 with a youth stock. He enjoys picking off soda cans at 50 yds on the range. I also have a 2 yr old but she already knows that she can't touch my guns unless I say its ok. She also comes to the range with us although she doesn't shoot. My kids all know where my guns are - especially the loaded ones. They've NEVER touched the guns except when I tell them to go get their guns for the range. In that case they each get their own respective guns and don't touch mine or my wife's.
Raise your kids knowing what guns are and what they can do - raise them with a good understanding of firearms and a healthy respect for them - and you won't have a problem with the kids shooting themselves.
Of course this is ALL in MY perfect world. Yours may vary quite a bit.
This is who we are, what we do.