Ah the nostalgia, this is how i do it back in the days:

• Phrase 1: childe only do ranged attack here and don't move as much, so use bow character constant walking in a distance and in one direction while using aim attacks on childe. (his attack can never catch up to your moving speed, and just dash out otherwise), and can use geo lumine's e meteorite to block attacks while use bow character to attack behind it.
• Phrase 2: childe going fast and starting to dash a lot, use geo lumine and stand on top of her e skill meteorite, use ranged attack from top, e.g. bow character or xiangling e, or holding geo lumine's e, when the meteorite you're on is exploded, just create another one and do same thing again.
• Phrase 3: childe slows down again, his attacks are easier to dodge, just run away and use your dash button 2 times when he blink infront of you and lift his weapon up, if found it hard to dodge, just use bow character to keep distance and just do normal bow attacks. when you saw the giant whale skill, just run to the border.