Ha, this was exactly like my first venture into benzo's and it was years ago. I ate the xanax, felt amazing. Then ate the valium(5mg i think), and passed the fuck out. My girlfriend couldn't wake me up and had to move my ass across the bed which I was taking up all of. I was breathing fine and stuff, so it wasn't like a worrying pass out, but she could not wake my ass up at all. I would just mumble and go back to sleep.
I suggest eating them separately unless you just want amazing sleep.