The correct pronoun for this sentence is the second option, "They're."
There - "The new restaurant is right over there!" In this sentence, "there" is referring to something that is distant from someone.
Their - "The cats love thier new toy." In this sentence, "their" is referring to something about two or more animals.
"They're" is combining the two words "they" and "are" together.
They are all coming to our house after the game.
They're all coming to our house after the game.
These both fit in the sentence, so therfore, "They're" is the correct option.
Your answer is "They're."
I hope this helps! :)