Are you on Broadband with AOL? You need an ADSL Router modem to replace your USB modem. This will provide a wireless network within your house and connect directly to the Telephone line. I don`t think it makes any difference being with Homecall.
You PC downstairs could connect to the router by an ethernet cable if you have a 10/100 network card installed. The two upstairs need to be wireless enabled either by using an internal card in each computer or a USB wireless adapter.
You don`t say what specs. the computers are but here`s a typical diagram. click here You can buy one from click here= This one includes one USB wireless adapter
There are many different router modems out there. The one I`ve shown you is probably coming to the end of its era because the MIMO (Multiple In Multiple Out) routers are more powerful in terms of wireless coverage but they will be nearer the £100 mark.
As for Parental Controls you`ll have to rely on AOL I`m afraid. There are no really good parental controls. Talking about AOL they will not offer you any support for wireless routers unless you buy it from them or upgrade to their Gold Package. Don`t do it! Whichever one you buy we can set it up with you.