Drumroll...
Be honest!
Hi Joan, do you have a second? Yes, I just wanted to touch base with you on filling out our taxes this year because they may involve the kids - see, Bill and I haven't had foster kids for quite so long before, and we want to make sure we have the tax info right so no one gets a penalty. Can you just tell me if you claimed them as dependents? That's what the state advised us to do, but I don't think that works if you have the deduction already, and we don't want to cause an issue for you. We would be thrilled to give you the difference if you didn't claim it yourself, we just want to make sure we didn't accidentally both skip the deduction.
Oh? Aw, thank you Joan. No, your hair looks nice today! Oh stop.
(bonus points if her name is Joan)