I think Crsytal would be your best choice for a child on a lux cruise. Oceania has almost nothing for kids.
Crsytal has a lot of childs programs ON cruises where there are kids. I see NONE on this cruise, whoever, if they book during a vacatiob period there should be many more.
There are kid's facilities, including a room with free X-box. I sneak in there and play it myself.
I think it is a good choice for the lux category, just make sure there will be other kids and youth couselors onboard first.