Unless they're super-fit and well acclimated, most people end up doing a portion of the hike in the dark. IMO you're better off ascending in the dark than descending in the dark.
I LOVE ascending from the Portal in the dark, especially if there's a full moon. The area looks amazing with the moon lighting up the landscape! It's also pretty cool seeing all of the headlamps ahead up you headed up the trail.
The only concern that I would have is making sure you're well rested, which may be difficult with a start at midnight. Lack of sleep may bring on AMS in certain individuals.
Is Trail Camp the only place you plan to refill? There's lots of water on the trail and I would recommend refilling more than once. There's no need to carry enough water to make it from the Portal to Trail Camp.
