I've been wondering about this too... does the size of the children matter? If I book a room with 2 twin beds or 1 king bed, my family (kids would be 3 & 6) could sleep reasonably comfortably, but I'm not sure if the hotel would actually allow it. Does anyone have experience in this kind of situation?
How about if I book a slightly upgraded room, which might be ~30-35 sq meters instead of the standard rooms which are around ~18-20 sq meters?