I'd probably suggest splitting it $600/$400. If there are 5 rooms, pay $200 per room used. Or another way to look at it if I were to go on cost per person, I'd charge kids less as in that kind of scenario, I'm assuming the kids would have much smaller rooms. $150/adult, $100/kid. Family with 3 kids again pays $600, family with 1 kid pays $400. If it were a standard 2 bedroom Villa at Disney with a couple staying in the king and a family with 2 kids in the 2 queens (not the living room), I'd think they should pay the same. A little more if the kids were to sleep in the living room.