M.W.
I think you should still go to some of the family gatherings and work on your own disapointment and anger towards them. I dont' see how they are toxic. Unruly kids need a nice aunt and some nice cousins to play with. If they are really naughty, say something right to the kid in front of the parents if you want, like almost what you would say to your own kid. Why do people have to discuss the nervous breakdown sister that is making stupid choices?
I think toxic families are families that are much worse than the examples you have given. I would cut off all ties from a family with a child molestor in it, for example. Or a family that gets so drunk at get togethers that they start throwing fists.
I think as long as you don't expect them to be cool people, and just roll your eyes in your head to the dumb things they say and do, and remember that everyone is annoying in their own way, you'll be fine. Let it go. You can't control other people. How are they personally hurting you?