Jeni and others are also getting prepared to visit the S-grade dungeon. Naturally, they would not be able to go inside that kind of powerful Dungeon, but with the help of Sam, they would be able to go inside the Dungeon.
Sam wanted to bring every one of them so that they could also get experience in fighting those Monsters. Also, he wanted to see how much they could progress while fighting those Monsters. This is the reason that he is also taking his friend inside the S-grade dungeon.
On the other hand, Gloria and the others are getting ready to go inside the Dungeon. Compared to the friends of David, all of them already have experience in fighting those Monsters.