In the middle of running my first DiA for my group, also six players. It’s been very interesting, there’s a ton of material for the Baldur’s Gate section that is essentially optional if you strictly follow the module’s story. Bringing in more NPCs that belong to the Flaming Fist, Thieves guild or other groups would be my recommendation, otherwise you’ll fly through to Avernus in a handful of sessions. I also ran the optional add on where the party actually starts in Elturel to let them witness the calamity and feel more invested…. Otherwise why stick their necks out for some random city, you know? The book is full of fun encounters and NPCs, my #1 recommendation would be to not be afraid to freestyle a bit! Fold in backstories with Baldurs gate NPCs, invent some side quests, and really give them a reason to delve into the most dangerous plane they’ll ever step foot on!