Is there a tactful way to raise the subject, or should I go for the blunt approach?
I'm a veteran of this, and I won't bore you with the details, but the answer to both of the above is, NO. There is not a tactful way to raise the subject except what you have already tried. Nor should you go for the blunt approach.
You can give the items to charity or someone you know can use them, and you can then choose to let your relatives know that you do this, or not, at your choice.
But why make an issue of it at all? Why not just enjoy the fact that they like to express their love in some way, and let it go?