After you connect your PB to the TV, you will likely need to go to the displays system preference and click on "Detect Displays". This will force the PB to recognize that you've plugged the S-video cable in. If the TV is a standard TV, then select 640x480 as the resolution. If it's a widescreen, select 720x480. Both resolutions should be at 60 hz. Depending on how much time you have with the PB-TV setup alone, you may want to calibrate the colors before giving your iPhoto presentation.
Being in a similar situation, I find using iDVD to make a photo slideshow easier then the direct PB-TV setup driven by iPhoto. Less to go wrong when playing a DVD using a standard DVD player.
Good luck.