The best way to know if a GSD is right for you? Visit local GSD clubs and meet the dogs in person, if you find one you like in both energy and temperament then inquire as to their breeder and contact the breeder and talk to them. Keep in mind good breeders normally have litters pre-sold before they parents are even bred so don't be disappointed if you're waiting a few months to a year before a puppy becomes available. Read through the Choosing a Breeder section, especially the stickies at the top regarding reputable breeders.
I really don't like invisible fences, firstly they really are not reliable for keeping your dog in and will do nothing for keeping other dogs/animals/people OUT from your yard. If you want a GSD I would definitely recommend a proper fence, preferably a 6' privacy fence. Expensive, but well worth it
GSD's are amazing dogs, they are very tough puppies as they are notorious for biting and can be stubborn which can be hard to explain to kids but yours are old enough it shouldn't be a problem. I would definitely recommend obedience classes, preferably with someone who has experience with the breed. Not all trainers are comfortable let alone know how to deal with them
GSD's are also extremely smart and do have lots of energy even as adults so most will not be comfortable with a simple fetch game for 10-15 minutes a day. They need mental and physical stimulation to keep them happy
If your family is active with walks, hikes, bike rides, etc then they can be a great companion to take along as long as when they're puppies you allow them to go at their own pace and bike rides should wait until at least one year old to avoid straining growing joints.
Jasmine - Female Miniature Poodle - born Aug 15, 2010
Loker Delgado Von Stalworth - Male GSD - born Jan 26, 2012
Koda & Zazu - 5 year old male cats
Alex - Male Cocker Spaniel (rescue) - RIP Cuddlebug 2007-2010