I got a free laptop with mobile broadband and while it's a decent enough laptop, the £30 a month is a killer for a 5GB download cap. Really regret getting it. Although when you reach that cap they don't charge you anymore. Just limit your service. Which is shit!
How about netbooks for the boys? Something like
THESE but you can get them cheaper.
Seeing how they are only to be used for web browsing and not games.
I learnt an expensive lesson with my girls. Got them a laptop each, but they over heated them after a couple of months due to leaving them on their beds.