A or not A in regards to theism

[FreeState]

I have a couple family members who have recently come out as non-believer. They both tend to tell people they are agnostic. I don't really care about what they label themselves - it is often safer to identify as "agnostic" than atheist.

What I struggle with is when I explain how I use the words with people not grasping my take on them. Maybe I've watched too many debates where they define the terms.

For me all propositions are A or not A. You are either convinced of a proposition or you are not.

So:

Is there a god?

Yes = you are a theist
No = you are an atheist
I don't know = you are an atheist

For me agnostic atheist does not make much sense as gnostic means you have knowledge of a proposition (knowledge being a subset of belief). So an agnostic atheist, while typically indication "soft atheist" (not accepting the claim there is no god) doesn't really make any sense - how could you have knowledge of something you don't believe?

I guess I'm looking for better ways for my lack of belief to be explained to people that don't have the same working knowledge of the terms (like my siblings). I am a soft atheist because I believe the proposition "is there a god" is unfalsifiable in general (yes there are gods I am a hard atheist on, but not all).