I use a VGA scan converter on my laptop, works very well...I can then connect hoster to the inhouse video.
I use the AverKey iMicro
4th one on list
http://www.aver.com/products/comptv.shtml
Connects to the monitor port on the laptop then > composite > a/v switch > RF converter > inhouse TVs
If you have to option of dual display the scan converter will work fine, if not it will just display what you have on your sceen I believe.
But if you need to get a vid card that supports dual display, might as well get one that has TV out as well.
Flip