A: That's correct it is a total cost of the resource for adults and kids. Kids age which are count as person can be set under resource. When resource allows 4 person and you have set kids age greater than 3 years old, you can choose e.g. 2 adults and 2 kids over 3 years old. Infants and kids below 3 years old are not being counted.
Q: Can't find booking calendar for the resources under back admin, how to set prices and availability on resource or listing:
A: To access booking calendar, click on resources folder icon next to the listing (Resource type) than click on resource title to edit details, prices etc. More information can be found here.