Hi there, welcome to Geeks to Go!
I'm not too sure on the laptop as part of the subscription, although I'm sure somebody else may be able to comment on these types of deals.
But with the broadband, no you can't run two accounts on the same line. For that you would need a separate line.
However, (and I feel this may be good news for you), if you merely want to have your broadband connected to both computers (your home computer and your son's laptop) then you can share this. To do this, you would need to purchase what's called a router.
Here is a link on routers with more reading than even I want

Common manufacturer's that sell routers suitable for home use include Netgear, D-Link, Linksys, Belkin, ASUS, and plenty more.
You can purchase a wired router, which connects from the modem and then splits out to each computer via a cable. Or you can purchase a wireless router, which usually works the same as a wired router as well as being able to cater for computers with a wireless card. Your son's laptop will most probably come with a built-in wireless card, as almost all new laptops do these days.
Finally, you can have an all-in-one device that is your modem and a router/wireless router all rolled up into one fancy little device. I have one of these myself (it's a Netgear, and I'm very happy with it), and when my phone wall-plug died in the office, I simply plugged the modem/router into the kitchen phone wall-plug and installed a wireless card into my computer

I suggest you call your ISP (broadband provider) and ask them what suggestions for a specific product they have. They may even be able to sell you one, or offer it as part of a deal. If ever you end up having problems with it, you would hate to find out that they won't provide any support for the particular model you purchased! Of course, you're welcome to come back here, we're more than willing to help out.
I hope this is helpful, with not too many "technical" words that weren't fully described!
Cheers
Troy
EDIT: It looks like I posted at the same time as Johanna! It's funny we've pretty much said the same things...
Edited by troy, 26 February 2008 - 05:33 PM.