First on the Table seating. They can shift you to a bigger table if you want.
Try contacting the line directly.
Or when you hit the ship go to the desk and ask when and where the seating changes can be done.
Second on the 2 - 20 year olds. - if there are a few others there's a lot for them to do that they want - as in nothing or something.
The singles group at the Disco or late night club. They do not let anyone under 18 in to this club after 7 PM or so.
They may be like my 2 slightly younger girls - stay up late get up later.
Hang at the upper level of the pool area.