You're exactly right. The Senate and House mailrooms will refuse to accept them and they'll end up being shipped to a warehouse somewhere and then we taxpayers will have to pay storage on them.
An alternative might be to send each Senator and Representative a taco. That might give them a clue.
Who cares, at least they will be spending it like we want it spent. And the bricks will keep coming. Someone will have to give the press access to the stash. Don't be a pessimist and I know what you mean but it is better than doing nothing but bitch.
So why not send a brick to DC, and also to their official offices in each state? Return receipt required on all of them.