Having spent six years with the animal control people on speed dial due to a situation I had with the dog next door, I very much feel your pain. However,of all the issues that local law enforcement people have to deal with, issues with dogs is one of their least favorite and most frequent complaints. There have been arsons, poisonings, vandalism and even killings related to the neighbors' dogs almost everywhere.
And I can see where you are wanting to go, which is, 'sic the law on 'em!" Preferably with three by five glossies and lots of video camera evidence that these dogs do, indeed, bark all the time. I myself had dramatic proof of abuse, abandonment and neglect, which meant that on cold miserable nights, the poor miserable (and very loud) dog barked and howled all night under our bedroom windows.
However, as you have found, it is tough to get law enforcement to respond. It is totally possible they have been warned, possibly even fined. That doesn't always help or change anything. And it is, as your mother very wisely realizes, a no win situation in which if you are the neighbor who raises all the issues, and they are fined or even if the dogs are taken away, or destroyed or whatever outcome you'd like to have, there are going to be some really angry people next door with an itch to retaliate, and the feud is on.
For the sake of your sanity, consider all the alternative solutions that have been suggested to you, like the noise cancelling headphones, if not for you, at least for your mother, who probably could use some relief from hearing the dogs bark also. Having the neighborhood nut cases think YOU poisoned their dogs is not a comfortable place to be.
If I were you, I'd back off from agitating quickly, at least stop talking to the neighbors about it. Because poisoning the dogs could very well get you sued or in more trouble with the law than having barking dogs ever could. And if they have reason to believe it was you, even if it wasn't, because you are the one who is making the most noise about the dogs, you have done exactly what your mother does not want you to do. You have put her in a vulnerable position where you have neighbors with a real grudge against you.
I will tell you one thing. Barking dogs don't hang around forever, and neither do bad neighbors. You may end up moving from there sometime soon, or the neighbors may end up moving, or they may decide not to keep dogs. Don't make this a hill to die on and don't let it destroy your happiness right now anymore.
