To begin with, please make free use of the writing resources (worldbuilding, too!) compiled at http://www.FoolQuest.com/fiction.htm But, for example, what else might be helpful for the science? And what about the business of show business? Indeed, how might this very task be better subdivided?
With all the planets encountered, what next? How can the series rap up? Any explanation for those gravity beams from outer space, that began the entire journey of the wandering Earth? How and why?
Beyond the gas giants lie the icy worlds of massive Uranus, then Neptune and tiny 134340 Pluto. The denizens thereupon use liquid gasses instead of water. It's cold out here! What problems for all involved, will be faced in the encounters? Will orbital artificial sun of the Earth, pose a danger to the denizens Uranus, Neptune and Pluto? Perhaps the Moon can be deployed as a shield, somehow?
After the inner worlds, the gas giants, failed stars, each in turn will certainly modify the trajectory of the Earth considerably. Who or what will be living in the high gravity conditions, sailing up in the atmospheres of the respective gas giants, and amid the many moons? What problems will be faced in the encounter? What about the eye of Jupiter and the rings of Saturn?
The Asteroid Belt is rich and prosperous, affording opportunity in preparation. So, how will dramatic conflict arise?
The third encounter will be with the planet Mars. Who or what will be living on or near the planet Mars? What will be the problems caused for both worlds by the encounter, and how can they be overcome?
Drawing away from the sun, Humanity on Earth will urgently need an artificial sun in orbit to sustain habitable light and warmth. But will that pose a danger to the denizens of Uranus, Neptune and Pluto, later on?
Will the encounter with Mercury come after that with Venus on the way inward towards the Sun, or before an encounter with Venus to come only on the way outward from the Sun? The dwellers on Mercury are silicon life, comfortable at temperatures of molten rock instead of liquid water. What will be the problems caused for both worlds by the encounter, and how can they be overcome? Obviously, the Earth will need timely protection from the heat so close to the Sun!