"Cocker rage syndrome" has been a topic of discussion for very many years, usually in solid colour (red or black) males - in the mid-'70s I worked with someone whose golden cocker male had serious issues that they were trying to work through with professional support, they had school age children and the dog was certainly triggered by them. I don't know the outcome in their case as I moved away.
I would never take on a 'rescue' dog unless I already knew the dog, the circumstances in which it had been living, and the reason for its rehoming. There only needs to be one ghost in its past for something to trigger either an aggressive or guarding behaviour, or cause a dog to bolt. It's hard enough for adults to be dog-aware, difficult for even committed and caring older children, and impossible for little kids. The dog can't tell you any frightening or upsetting experiences it had before whichever charity decided to get involved. Especially with dogs that have, by all accounts, been to hell and back in Cyprus or Eastern Europe, I think placing them in inexperienced homes, or with children, is asking for trouble, and it's no wonder so many end up being returned to the charity. The charities are actually funding big business with the people running the kennels which send van-loads of dogs over here for rehoming. I'd always prefer to get a puppy, from a breeder and dogs I already know, or know of, and be certain that nothing in any way negative has happened during its crucial period of socialisation and fear responses.
Hard as it feels now, I'd agree you made the right decision.