A few more dream ideas! Hope these help.
Since Latias and Latios are both good at illusions there dream could be them as magicians doing a show together and final trick needs a volunteer the MC and the would magically inflate their belly's then take a bow.
For Zapdos she would dream of playing an electric guitar on stage with the finally blowing out all the lights.
Moltres could dream of being a top chef and yelling at other chefs for making it raw or overdone. The MC would be the VIP customer she is cooking for.
The Lake trio could be oracles saying a prophecy to a hero.