Ohhh, you are doing the one-day hike? Major respect to you, I wish we had the stamina to do the full thing in a day. At night it certainly will be easier to find people as you'll see headlamps all over the place. The last time we started at night we had a solo hiker join up with us once we all got spooked by what looked like a predator's glowing eyes looking down at us from the switchbacks near the start (turned out to be a deer after spending 10 minutes of yelling at it).
Also, you may already know this stuff but be mindful of those bears at night around the portal, those guys are real jerks. On our trip last month we met a lady who claimed a bear snagged her backpack that was leaning up against her leg in the parking lot, she lost her phone/garmin/food, everything, and the poor lady was still trying to still hike up carrying a shopping bag with what little she had left. There's a Youtube video posted just a few days ago showing a nice fat bear up there having its way with someone's stuff: https://www.youtube.com/watch?v=Pwof7KtI1cw
I hope you find your group, I'm betting that you will. Be sure to post some pictures if you go!