I am having trouble discerning if your comment has a derogatory tone too, I don't think it's OK to "open and honest" about "everything" with children.
Only what is appropriate for their age
There is absolutely no difference of what is appropriate to divulge to children between poly and traditional relationships. I personally would not stress my children out about finances. That is a parents job and certain things I don't divulge to my children because I believe kids should not be burdened with adult life.
I understand that there is bitterness when people end relationships, but I personally believe that when a person goes to a child and questions them about their parents intimate relationships, that is extremely vindictive, and it's that behavior that is the abuse.
People justify their hatred and it's pretty disgusting when they justify confronting a child about things.
Do either of you honestly believe that a child would come up with such questions on their own?
Do you seriously believe that when the child does question their parents that it wasn't brought up by some adult who is upset, bitter, or full of hate?
Unfortunately sometimes it is appropriate to educate a child that there are vicious people in the world who would do such a thing, so some parents do have to inform their children about the ravenous wolves who wear sheep's clothing.
That's just life, but hopefully society is reaching a tipping point where it doesn't matter if you are poly, gay, black, any kind of person, when we all refuse to tolerate subtle hatred, we can change the world.
Because that is what it takes, even when we have laws written to protect against hate, we still have to combat the subtle attempts to marginalize minorities.