Good question Dave....we've discussed this topic several times ourselves. It's a topic that never hurts to be repeated.
Photos themselves are not acid free. We place them in an acid/lignin free environment to help prolong their life. Therefore to answer your question about whether you need to to somthing to them to de-acidify them....I'm not sure that you can do that. I'd say start by getting those photos out of that environment (Un-Do) is a very helpful product for doing that but doesn't seem to work real well on liquid glue type adhesives.
Your best bet might be to make new copies of those photos, then start your new albums.
When I first began scrapbooking, I attended a Creative Memories workshop. They teach that you can put acidic things in your album (such as newspaper clippings, or other memorbelia) as long as they are not touching your photos. They also say that their paper is acid and lignin free as well as buffered. Which is supposed to help in the preservation process. You can, however, overlap your memoribelia on the corner of your photo as long as you have acid/lignin free paper between the memorbelia and the actual photo. Does that make sense? With this in mind, I'd say just make sure those older photos are not touching newer photos. There is also a product on the market called Archival Mist that you can use to spray memorbelia. It helps eliminate some of the acid. I do not know if it has even been used on photos though. Hope this helps a little. I'm sure you will get lots of good responses to your questions. Good Luck with your project and welcome to the group! Susan