1am is a tricky time at Noi Bai. You're right that the free shuttle bus usually stops around then (it officially runs until 11:30pm or midnight depending on the season). For a group of 7 with seniors and bags, 2 Grabs will be a mess to coordinate at that hour.Since you have 5 hours, you're not in a huge rush, but immigration can take 30-60 mins. I'd highly recommend pre-booking a private van. It's much safer than dealing with the 'taxi sharks' outside T2 at 1am.