I have a scanner, Mac and old photos I want to scan. What's the best way to proceed?

They’re old family photos. I’m looking for decent resolution. I think I’d like to keep them at their original size, if possible? Does Photoshop do this, or is there some application anyone can recommend? It’s a Canon scanner and I’m using Mac OSX 10.8 (if that’s a factor.) Also, if I need to spend a little dough (and I’m mean little, so be it!) Thanks.