Perfectly feasible if you can get to grips with installing hardware.
You'll need a router (probably wireless) that works with your modem -- or replace the modem with an integrated ADSL modem/wireless router (generally called a wireless router). I'd talk to AT&T first and see what they recommend.
If you're going to use wireless the kids' computers will need to have wireless adapters -- most current laptops have them built in but adding them is relatively simple.