About the 7 Children of the Prophecy, I think it's Percy who will lead the other 6. And I think that these names are the ones who will be in the Great Prophecy.
1. Percy Jackson=Son of Poseidon/Neptune
2. Jason Grace=Son of Zeus/Jupiter
3. Annabeth Chase=Daughter of Athena/Minerva
4. Nico di Angelo=Son of Hades/Pluto
5. Piper Mclean=Daughter of Aphrodite/Venus
6. Leo Valdez=Son of Hephaestus/Vulcan
7. Frank Zhang=Son of Ares/Mars
These are just my best guesses. And i hope that they are also the destined 7 demigods of the prophecy.
Thanks for reading :)