This man is made for TV. Why would you EVER suggest he "write a letter?" LOL.
Send them a letter. That’s how it was done by the president initially.
Then, to pick up on your “made for TV” point, read it on TV from the Oval Office on the date and time of the address. Do not give them any sort of common stage for their antics.
Make sure the Republicans do not show up for the joint session. (RINOs, who cannot help themselves, excepted.).
Let the Democrats entertain each other with their theatrics.