if everyone in the house just uses AIM, or checks their mail, it may be enough
I don't even remember what 56k was like.
I used to have dsl long before i ever got cable, and i still remember THAT being far too slow, even just hooked up to a single computer.
I don't know what your budget is, but i get my roadrunner for $30 a month through school, which is a pretty good deal if you ask me.
It pays for itself over and over, in my opinion.
and if your parents already have cable, adding roadrunner is only $35 a month extra if you buy your own modem (i bought a wcg200 for $79 at compusa)
and if you just get the slower 3mb/s package, i believe it's ony $20 or $25 a month.