I've managed to persuade the Githyanki to leave me in peace. And I had Lae'zel in the party (she rushes off to talk to them). I just got her to lie to the dragon rider about their purpose and not tell the truth (and passed a Persuasion? check). The problem is then that there is no dead Githyanki and no breastplate drop to lead to the location of the Creche (that I found out about later on a bg3 wiki) - but I believe this happens in Act2? so outside the scope of the EA in this case.
