&Shiney*, I hope that you know that in no way am I belittling what happened to your son. As I said at the time there WAS a reason for the incident - lack of adult supervision and common sense when children were running around an unknown dog in a small, enclosed environment.
Celestial, my kids have had dogs in the home since the day they were born - in DD1's case a first cross Collie and we've had a second collie cross too. Both were perfect. My DDs are now 14 and 15 and are rescue volunteers. They've been so for about 3 years in an environment where we rely on common sense and not strict H&S rules so they interact with literally scores of dogs upon each occasion... and they have never been so much as snapped at in their lives.
You see, for every bad story and warning I can give you fifty good stories to counter them. I'm a rescuer and a hands-on rescue volunteer - I can tell you about F, the ex rescue Collie who's now in a home and doing wonderfully, about J, theh Collie X Springer living with 2 DC and regularly seeing a baby grandaugher, about R and J, two of the most well behaved Collies you could wish to meet... dogs I know personally and which give a completely different picture to the one being painted of the breed above.
But at the end of the day it's all anecdotal and anecdotes do not represent fact or statistics. Or otherwise I presume that you'd all go out and adopt a pair of German Shepherds and a Lab cross because I can give you examples of how mine don't nip or herd my children? Off you all go then, that's GSD Rescue's problems solved. Doesn't work like that though, does it? Yet you'll consider giving up on your dog because of a single example given to you by someone else? 
QuietTiger is right and I'm pissed off too. "Collies are not bad & difficult dogs, they are SPECIALIST dogs who are not really suited to a novice dog-owning environment where they are not mentally stimulated and worked." is spot on. I totally support everything she says and urge you too to speak to Wiccaweys before making any decisions. Rescue tend to be very cynical about many of their fellow rescue organisations and, forgive the pun, can be very bitchy about them... but Wiccaweys has virtually unanimous respect from every rescue and rescuer going. I've been involved in rescue myself for many years now and would support and recommend Wiccaweys wholeheartedly.
On another note may I warn you - contrary to your comment up there somewhere your breeder is not a responsible one. A responsible breeder would never have placed an adolescent collie with a novice in the first place, particularly not one with a small child... not because of any danger to the child but because they would know that so very often energetic, demanding dogs end up unwanted by families with young DC, who feel they can't cope or they haven't the time after all, just as is beginning to happen here.
A responsible breeder would also have bred only to improve lines, would have had a home booked for her before they even mated her mother and wouldn't just have decided that they didn't want her when she was 12 months old.
They would also have guaranteed to take her back at any time in her life if it didn't work out, not told you that they'll have her back within a month but after that you're on your own.
This is why I urge people to go to rescue to adopt and not to take on a dog from numpties. A decent rescue would never have given you an adolescent Collie in the first place, would have homechecked you for YOUR benefit as much as the dog's, would have given you an assessed, spayed, vaccinated and chipped dog who was suited to you and been there to take her back if ever you couldn't keep her.
And, if you hit a problem, you'd be getting advice from the rescue right now, who would still be there to advise and support you in 12 years time if you needed it.
This is not an unresolvable problem but because you're a novice owner and you're concerned for your child and have been scared shitless by horror stories it just seems it. It's understandable that you feel overwhelmed and that you can't see the wood for the trees but Wiccaweys will help. Please... give them the chance to do that.