If you are in the 788 i will change the seats, since row 4 is behind the door. So your choices are to board last or you will be disturbed by the Y pasagers.... now i will say that row 5 is worse on the middle seats, since more people will pass by your seat from one side to the another, also row 5 on 788 you will get a lot of noise from Y
Row 4 could be OK if you are on Windows seats since you wont have people walking on your space. If you want middle seats go for row 2 or row 3, for me is the best on the 788. On row 2 you wont get a lot of space over head, but you will have a lot of storage on the sides. .. Row 1 will be more noisy for the kitchen.
You should get a full dinner as told above you may get all together and you also may not get a cheese plate (happend twice on late flights)