I am going with Alex and Hope being same year as Fleur, so I could let them meet.Since I disliked the whole Bill x Fleur pairing, I mean she was treated so badly by Molly, Ginny and Hermione.
So next thing is which school will they be attending, it is Ilvermorny School of Witchcraft and Wizardry.
I don't know maybe Hope will meet Hermione during her visit to France.I can add stuff like that.
But Harry is not going to helped a lot,since the Mikaelsons all feel it will be too much trouble.Since Harry will be closely guarded by Dumbledore who will only annoy them.Maybe Hope and Alex will intervene and it will be probably during the 3rd and 4th year.
Also, since Elijah, Kol, Freya and Davina will be coming to this world first with Alex to set up a good identity and they will turn to immortals similar to Slias,thus being able to do magic.
Elijah will be into the business and political field,while Kol in potions and Davina an Enchanter and Freya is all rounder.
The Mikaelson family will be in there for 10 years and create waves among the magical community.
To make sure no one questions are asked about there heritage Alex will do a modified version of the spell Doctor Strange did, Instead of removing a person from the memories it will add them.
It is almost similar to reality warping.