Araujo seem to unfortunately be quite injury prone, so I would not risk starting either him yet. Dembele surely isn't ready for more than 30 minutes yet as well. With an abundance of great midfielders, and us needing to be in control of this game and not let them or their fans into the game at any time (or it could become hairy), I would actually stack the midfield, and put Dest back on RB, enough with the RW experiment, he clearly doesn't have what it takes on the offensive side. But I would start him ahead of Mingueza, since we need both full backs to be more attacking with just two up front. And that way we also don't have a crisis in the centre, can have both Mingueza and Garcia there, pair them up at CB, if we're not ready to risk play Lenglet and watch him fuck it all up, cause you just know that with him and ClownStegen both there, this is the perfect game for them to give away a penalty in the opening stages. And if we concede first, then we're pretty much fucked. If push comes to shove, I would actually risk Araujo rather than play Lenglet, but if Mingueza and Garcia are available, I'd start them first and have Araujo on the bench just in case.
Up top, I would put Ansu and Memphis both centrally and play a 4-4-2 diamond, with Gavi or even Puig as the advanced midfielder. Would start Nico as well alongside Busquets and FDJ, no need to risk Pedri right away. I would sub him on alongside Dembele (and one of Gavi/Puig, whoever stays benched at the start) in the 2nd half. As for the result, I'm gonna be optimistic and go for a 1-2 win, have a feeling we will go 0-2 up, and then stupidly concede in the last 20 minutes (Stegen probably gonna concede their first shot on target again), but then just do enough to hold on and scrape up a win.
Then hopefully we also beat Benfica two weeks later and make it out of the group before facing Bayern, that way we can go there without pressure, with mainly youngsters and make it a great learning experience for them, since we'll get battered in any case probably.