In terms of room size and basic amenities (queen beds, double sink) the rooms are the same. The Royal Rooms are decorated with a princess theme. For example, the bed spread and shower curtain have a jewel print, the headboard has a bayou scene (Princess and the Frog) with fireworks that light up, and the walls are decorated with Disney princess paintings. It is very cute for young girls. My DD7 loved it the first couple days, but then the novelty wore off. I'm glad I went once, but I would not get a Royal Room again, its not worth the cost in my opinion. In your case, getting two is even more costly.
Since you have a family of five, depending on the ages, you may want to consider getting a room in Alligator Bayou section of POR, since they can accommodate five (with a smaller child sleeping on a murphy bed).