I have summited Washington many times in the winter and have also been turned away at Lions Head a couple times as well. Here's my two cents:
Cliff bars will be hard as a brick, bring chocolate bars or something fatty that won't freeze too badly and keep in chest pocket. I like to get some calories from juice as well or something, makes a delicious slushy up there.
Bring an extra pair of goggles or use cat crap, you'll be warm from hiking for several hours and end up with a layer of ice inside otherwise.
Most parties that are struggling up there appear to be wearing way TOO MUCH. Consequently they end up with the problem of heat management and have to slow down because they are out of shape or too warm to speed up. Remember this is a walk-up hike, more or less. It is not uncommon for parties to summit and make it back to log out in less than 6 hours comfortably. It's great that you are well prepared, but I never bring my sleeping bag.
The last two times I summited comfortably, I was only wearing a breathable softshell, balaclava, and two layers beneath. My point is that if you are moving you will be warm, even in high winds and -15 temps. And if you're in shape, there is no altitude to slow you down so you can move pretty swiftly up there. Have fun! Maybe I'll see you up there!
PS: On the weekends it's downright BUSY with hikers. Get an early start!