As for Ligue 1, I'm sure Enrique won't have any problems, but PSG also have to play Atalanta on September 18 and Barcelona on October 2. This is really bad for PSG. As you said, They will play Gonçalo Ramos and Barcola as replacements, with Kang-in Lee as a substitute. Ramos actually has a primary position as a forward, but he's been overshadowed by Dembele, whose contribution has been extraordinary in the striker position. We'll just have to wait and see if Ramos can make the most of this opportunity.
It is true that for the league they won't face that much trouble, but when it comes to UCL they may actually have some trouble. Dembele and Doue are very important two players for this team, one of the most important ones, so missing them both would be an issue for them.
However, it's not "that" long, 1.5 months and 1 month isn't that much of a huge time and we can see them play soon enough, so they won't be missing that much time. That would be still start of the league give or take, and that would also be not that difficult, considering what they will be doing, and UCL will have just few games that's it. So they can be back right on time for them to keep doing a good job and keep getting the wins they need.