"What do they include in their dinner?"
Translation:Τι συμπεριλαμβάνουν στο δείπνο τους;
I'm not sure what the formal rule is, but I think that if you have a WH- question word, the verb needs to come right after it. (Though if there's an unstressed object pronoun, that comes before the verb as normal.)
Αυτοί τι συμπεριλαμβάνουν; Τι συμπεριλαμβάνουν αυτοί; both work for me.
But not *Τι αυτοί συμπεριλαμβάνουν;
Similarly with Πώς θέλεις να μάθεις εσύ; or Εσύ πώς θέλεις μα μάθεις; but not Πώς εσύ θέλεις να μάθεις;
Or with an object pronoun: Τι του δίνεις εσύ; Εσύ τι του δίνεις; (with indirect object) / Πού τον είδανε αυτές; Αυτές πού τον είδανε; (with direct object)
I would translate "ποια συμπεριλαμβάνουν στο βραδινό τους;" as either "Who do they include in their dinner?" or "Which ones do they include in their dinner?". The first refers to a woman or an item that's a feminine word in Greek, while the second refers to a known list of things (neuter, plural). That's not as close to "What do the..." in my opinion. The literal translation "Τι..." works very well in fact in this case. :)