Wow, burning, you must not get out much, to bother tracking back how many posts it was since OP admitted fault. If you use those eagle eyes of yours, you'll notice that I also acknowledge she admitted fault, good for her. But yes, if I'd just been knocked over someone's car door by their child opening the door, I'm afraid adrenaline and shock would probably make me consider the child pretty stupid.
However, yes, the point does unfortunately deserve ramming home - not to OP necessarily, who appears to understand that it could have been an even worse accident, but to a massive number of posters since who seem to think (like you) that it's all ok because "kids make mistakes". In this case, fortunately, they ended up with an angry, bruised cyclist and nothing more. However, there've been multiple cases of dooring where the cyclist has been severely injured or killed. Were that my OH or a friend, I'm afraid "children make mistakes" wouldn't cut it as an excuse.
The adult in charge of the vehicle ultimately should also be in charge of the child and should either put child locks on or remind the kid to look before opening the car door, or get out on the pavement side. It's common sense for the safety of the child themselves, after all, and certainly something I remember being taught as a child.