I have 3 dogs and have friends and aquaintances with as many as 8 so no, it's not that much hard work if you're a dog nutter like us.
There's no reason why rescue wouldn't consider you just because you have small children (speaking as someone who assists in this area here). The bigger ones often have set in stone policies but the smaller, independent ones are often far more flexible and are able to decide on a cae by case basis depending on the family and the dog in question.
If you go for rescue, seek out one which vaccinates, assesses the dog before rehoming, neuters as standard unless a vet advises otherwise for health reasons, offers lifetime support, will take the dog back at ANY time in his life if you can't keep him AND which homechecks, which is for your benefit and that of your family as much as the dog's.
If you go for a breeder please DON'T look for a crossbreed but only seek a purebreed pup or older dog through the BREED CLUB. KC registration alone means nothing, 90% of puppy farmed dogs are now KC reg, sadly. Be prepard to wait, a good breeder will only breed when he already has homes AND a reserve list in place and will breed only to improve breed lines with all health checks upon parents and pups carried out and available in ORIGINAL format, not copies. Never touch a breeder which won't question you to within an inch of your life, who can't talk genetics til you fall asleep from boredom and who won't take a dog back at ANTY stage of his life either and bear in mind that:
A good breeder will generally show and will have bred with the intention of keeping a pup to do so.
He will only breed his bitches very rarely, will not make a profit from it and will never breed a bitch younger than age 2 or older than age 4, 5 at most.
A breeder MUST be registered with his council if he breeds more than 4 litters in any 12 month period - contact his council and ask if he is registered.
A good breeder will ONLY breed one type of dog. If he breeds more than one breed, avoid.
A good breeder will NEVER advertise on epupz, Pets4Homes, Gumtree, shop windows, free ads and similar. The aforementioned websites are full of puppy farmers and backyard breeders (backyard breeders are the type who breed to make money/because their dog is cute/because they want the kids to see pups in the home - these BYBs don't carry out all health checks, don't choose the BEST stud dog, just the cheapest or most convenient and won't be there for you if you need help or can't keep the dog in 10 years time).
A puppy farmer is a bugger for the unaware to spot these days. Many use "normal family homes as a front for their businesses and fool potential owners. Hence always go via the breed club to find a reputable breeder.
All that said, there are thousands of dogs in need of homes in rescue, many coming from family homes with a history behind them and a good rescue will assess the dog regardless. Please remember, last of all, that it's not the breed that's important, it's the dog which is right for you. Take it from the woman who, having lost her dear little 12 yo collie cross to cancer went looking for a similar sized, same sex collie cross of about 4 to 6 years of age... and came home after much searching with a ruddy huge long haired white German Shepherd boy of 9 years. Not what I was looking for in the least but, although I've owned and fostered many other dogs since, THE most perfect dog for me and for my family that I could ever have wished for and I know I'll never find quite so perfect a match again.
I'm very biased, I fight to stop dogs being killed in pounds and by uncaring owners... but, all I can say is that find the right rescue and THEY will find YOU the right dog.