Open up iMovie, add all the photos you want you may need to extend them a bit, add a couple of transitions and you are done. Then use iDVD or Toast to create the slideshow.
If you don't add transitions in iMovie the photos might come up a bit fast.
Why not just click on the IDVD Button. You can add up to 99 photos then you can set the slides to auto play and give it an amount of time before advance then you have a slde show.