Remember....
.... they don't have any power over you, except you give it to them.
Train it many times (not only for this blood card matter but for all the matters concerning elders).
Elder: "We need a copy of your blood card." or "We need to talk to you in the backroom."
Awake JW: "My dear brother, Thank you so much for your concern/help/personal interest. I appreciate it very much that you care for me. BUT NO. I DON'T SEE IT NECESSARY THAT YOU HAVE A COPY OF MY BLOOD CARD! / NO, I DON'T NEED YOUR VISIT RIGHT NOW. If ever I see the need (for having my bloodcard / visit) I will let you know."
Train it often so that you can say it in your sleep. Then enjoy the reaction on their faces.
They might ask further but you need to stick to it.