1 Ryokans might give you a slight disount if your children sleep in one bed /futon/ with their parent
2 You must make a reservation and you may even have to pay a deposit
3 You can order a western breakfast the night before unless you enjoy raw eggs, rice and seaweed in the morning
4 Love hotels are the place where Japanese get little privacy, but you have no place to leave your children. For five hour stay the price is 5500 ~ 6500 JPY and it's 8500~12 000 JPY per night for two people. Love hotels you can find in Shibuya
5 In Disneyland you may have to wait long time to get on one ride especially in the weekends