I'd use QuickTime Broadcaster (and, optionally, QTSS). There's a couple ways to do this; one with just QuickTime Broadcaster, and one with QuickTime Broadcaster plus QTSS. Both will require QuickTime at the other end.
To use just QuickTime Broadcaster:
You'll need to know the IP address of the computer at the other end. If your parents have a cable modem and a semi-unchanging IP address, this would probably be a good option (If their IP address changes all the time, and they/you don't feel comfortable getting it, then the option with QTSS may be better.) Simply set up your broadcast the way you like it, Audio, Video, etc.; you can use the defaults for several presets, such as Modem, Cable/DSL, and so on. On the Network tab, choose Manual Unicast. Enter the IP address of your parents' computer. Click Broadcast. Choose Export SDP from the File menu, and save it. You'll have to email that file to your parents. They should be able to open it up right with QuickTime. If your parents' IP address doesn't change, all they'll have to do is open that file with QuickTime whenever you're broadcasting, and that's it! Each time the IP address of their computer changes, however, you'd need to export a new sdp file and send it to them.
To use QuickTime Broadcaster and QTSS:
Install QTSS on your machine. It is accessible at http://localhost:1220/
). Set up a username and password and log into it. Check General Settings, and then Change Movie Broadcast Password. Give it some username/password that you'll remember. Also, set the server to start as system startup time if you wish. Once this is set, log out of the server. You're done with QTSS.
Then, open QuickTime Broadcaster. Instead of Manual Unicast, this time select Automatic Unicast (Announce) on the Network tab. Enter your local computer's real IP address in Host Name, since that is where QTSS is running. Give it a name, like mystream. Enter the movie broadcast username and password you created in QTSS. Click broadcast. Under Location, it will say something like "rtsp://blah.whatever.com/mystream.sdp". That's what your parents can enter into QuickTime's Open URL... box. That's it. They can then use that same URL to view whenever you're broadcasting.
If either end is behind a router/firewall or other garbage, this of course becomes ridiculously complicated and not worth it. Good luck.