OMG... where did I condemn the OP? I said I feel sad for her, the child and the dog... I feel in a way she failed him, because she took him on in the goodness of her heart, without thinking it through, Dobes (as I know) are not a breed for the novice and I would not bring an unknown full grown dog in with my three year old child! Thats my feelings on it...
I feel sad for the OP because she is stuck in a no win situation, sad for the child, he may now have that fear, I hope he won't, sad for the dog, pushed pillar to post..
Would I take that dog? No, simply. He is dog aggressive, I have 3, be a bit stupid of me to take him on, would I if I didn't have my 3 dogs, yes...!
No the child wasn't to blame, I also didn't say he was... I feel desperately sad for all involved and think if someone had worked with that dog before it got to this situation, he would not face a death sentence.

Broadening this discussion out a bit (because we don`t know what the OP has decided) - I can`t help thinking the automatic destruction of any dog that bites is an over-reaction.
I have 4 dogs and 3 of them have bitten people. Not badly, and all under extreme stress. I am missing a fingertip because a friend`s dog bit me during a dog fight. I have a scar where a previous dog bit me when I was lifting him off spiked railings where he was impaled.
If a dog bites it is because it has / is being mismanaged or badly handled, as a rule. Just as when you get kicked by a horse or trodden on & jostled by a cow. I should not have intervened in a dog fight, and should have muzzled the dog in pain. So it was my own fault I got bit.
The fact that a dog has bitten does not make it a `bad` dog. It may well be that the dog has too many problems to save, but that`s not the fault of the dog.
Dogs do not know that children grow up to be `proper` people. They do not know that these short, unpredictable creatures deserve special treatment... until they are taught it. It`s like blaming a feral child for not behaving properly.

Agree. Woody bit my husband, bad.

We assessed the situation, realised it was our fault and that he was (rightly) food guarding. We hadn't handled it right and so we worked with him on it and it hasn't happened again.

He growls alot when he doesn't get his on way and will try to bite (snap) during certain 'procedures' (eye drops etc), but again, we work with him and muzzle where necc'.

Granted he has never attacked us, but he has been quite an aggressive young chap in the past.

Should we have had him pts? Or does it only count if a dog bites a child?

I agree C&D.
I took Reah on knowing full well that she was people aggressive, having bitten several people and killing another dog.
In those days though my children were grown up and one had left home.
I feel for the little boy and the OP children can not be watched 24/7 with a dog of any breed (I know this with Foster kids) we work hard with the ones we have but you can always rely on one to break the rules, thats why it is important that the dogs adhere to them
Thats why I said that I thought whilst she had the dog to keep a muzzle handy for when child and dog were together.
Dogs can be turned round with the right person and time, but thats the thing time is needed.
If I were to have foster children/small children of my own when I took Reah I'd of never of managed it, I can safely say she would of been PTS.

It wonderful to take a dog feeling you are rescuing it, but one has to be practical IMO and look at the wider picture, ie experience, time, dedication etc.,

I hope for all concerned things have been resolved whatever the outcome, but I think no-one is to blame, including the dog, its one of those sad affairs.

Any breed!

Why?

What age can someone take on an aggressive dog? I hadn't realised there was an age limit.

Some people are very small minded lol..dont let it bother you! I have posted about the dog we have here that was aggressive, she wasnt aggressive towards my mum so there was no point my mum working with her it had to some one that she would snap at, im pleased with how far she has got and thats all that matters!

If some one is 'willing' to try i dont see the problem, but hey some people think its best to end the 'problem' instead or before trying to resolve it

I have stumbled across this which I fear is the branch this dog possibly came from..

We DO NOT rehome dogs to a household if there are children residing there aged 5 years and under

This should have been made clear by the previous owner from the outset, this dog should NEVER have ended up in this home, those rules are obviously in place for a good reason.

http://www.rspca-preston.org.uk/adopt_a_dog.php

Absolutely agree. I am very curious to know how much the previous owner knew about the history. Although I suppose it could have been a total one off, first time thing? Couldn't it? Unless it was the only person to blame in all of this was either previous owner or RSPCA. NOT OP, NOT CHILD.

I bet in a population of over 6 million there is more chance of someone being in a better position than a forum of over 300, most of whom have dogs and kids.

My point being, just because we can't, doesn't mean someone can't.

There you are then.