The problem from what I have read is
-The new kids behave differently
-The new kids are being excluded by the rest of the neighbor kids due to the fact that they're different. (could be their behavior, could be because they're new...)
-New mom is upset and wants her kids to fit in.
-OP, not sympathetic. I say you're not sympathetic because you have spoken poorly about the entire family and made assumptions before you got to know them. Ridiculing them for their home purchase. Who cares if it sells or not. The market is changing. So that is non of your concern.
I understand why you felt it necessary to throw out that they were adopted, sometimes it's hard to gauge what a child has really gone through and you can't always tell if their lives were traumatic or pretty normal. However it's still sounds terrible to say it. It is true that some adopted kids can have behavioral problems... Just as it's true that a Good Mama, can raise a bully and a brat without being able to blame someone else.
I've had neighbors that make me want to run for the hills. And instead of being part of the neighborhood clique I tolerated their different behavior and I made a strong effort to be "GOOD" and "FAIR". When I say tolerated, I mean I dealt with strippers and the fundies without being rude and always treated them with respect. Because get this... ready? THEY ARE PEOPLE! With feelings and emotions. Just trying to find a good place to raise their family. And it sounds like to me they struck out.