What ship are you going on?
It absolutely depends on your budget. Personally I would have concerns with such young children in a balcony cabin. Outsides and insides are great with a choice of two lower and two upper bunks or two lower and a sofa bed.
No Problem we have cruised with a 10 & 15 year old in pullman bunks with P & O ,We would not want them in a room on their own and of course that would be double the cost ,so depends on your budget yes bit tight !, think if you are in your cabin you not enjoying your cruise and with children your age the Kids club should be fab !remember your steward does all the making and putting away of beds daily .
We stayed in an inside cabin, there were 4 of us, two adults, my 12 year old son and my 2 year old daughter.
You are hardly in the rooms so I wouldn't book a room above your budget.