It is unlikely that the problem is due to using a Netgear router instead of Linksys, or that changing would necessarily make a difference.
You don't say where your PC is in relation to the router but, unless there is a particular reason for connecting "wirelessly", use an ethernet cable instead. A "wired" network will always be faster and more reliable.
As regards your son's connection, it may depend on what lies between the router and his wireless adapter. I read about someone in a new house which, for thermal insulation, had the walls lined with an aluminium foil - this rendered wireless networking impossible. Other things to check, avoid having cordless or mobile phones close to either the router or wireless adapter(s), avoid locating them close to large metal objects, in particular central heating radiators. Try changing the Channel number in the router's settings.