How to throttle usage of individual computer with Apple Airport?
Apple's hardware doesn't perform Quality of Service  - so you'd want to install a router that has QOS between the AirPort and the internet connection.


http://www.howtogeek.com/75660/the-beginners-guide-to-qos-on-your-router/


If all the children are on Mac or iOS - you could install a network link conditioner, but that is generally harder to administer and less effective at letting faster access when there isn't contention on the connection out of the house.


How to simulate slow internet connections on the mac


Before you select a new router, you'll want to determine what the total network speed is for the house. Optimizing for 10 users on 6/1 ADSL service is going to be harder than 4 users of 100 MB or fiber. The tools are the same, but the decisions you make and the end results will vary.