Anyway, you certainly can request through
DCL or your TA (whomever you booked with originally) to have a table of 4, but they can never guarantee it.....
What I do is when we board we dine in Parrot Cay for the buffet as opposed to the buffet up on Deck 9. For lunch that day it is open seating, but we hunt around the dining room for our table number (which will be printed on your KTTW card). Once you find your table you can see what size it is. If it is a larger table you then can go to the dining changes venue to see if you can change your table to a table of 4. When and where to make dining changes will be printed in the Navigator you get at check-in.