I have an old HP model NX9010 laptop which has 1gig ram and a decent hdd. I want to set up frugal puppy on it for use by my 11 year old granddaughter. The laptop is intended to be used to do homework on such as math and essay's and yes to find answers to homework questions via for example google. The catch is that there is no landline in the household and I am going to give them a usb mobile dongle such as either a vodafone k3715 or a 2degrees-mobile unit (haven't decided yet pending coverage research) and do not want the kids to get sidetracked and go youtubing for video's and other such high data usage stuff so I want to know if I can block access to youtube and or any other site I (or her mother) deems not appropriate for the 11 & 6 year old kids to get to.
If I can do the above .... HOW ? keeping in mind that I am a noobie puppy user and although smart enough to pick things up rather quickly still need a helping hand in the where do I start department

Any guidance gratefully received and thank-you in advance for help offered ....
Location = out south in the rural outskirts (about an hour out) of Auckland, New Zealand