Hello Mark,
I am a few weeks into a similar project: scanning in many negatives, transparencies and a lesser number of prints. I have come across the following (obvious?) issues:
1. Storage space: do you have sufficient 'storage space' for this project?
2. Backup: with all this important family history, again have you allowed for the storage requirements for a backup copy of your work?
3. Scanning Resolution: I am not familiar with the scanner you are using, but the scanning resolution seems quite low for (35mm?) negatives and transparencies, particularly if you want reasonable sized prints. I really think it would be better to scan at the highest resolution device you can lay your hands on! (>2900 dpi?)
3. Output format: I understand your decision for the TIFF format, but, if you can, get the scanner to output an additional , smaller, JPEG version of each image
4. Scan time: I've found that it takes around 5-7 minutes per scan irrespective of scanner, software, computer etc. It takes time to load the image, scan, have a quick look, tweak a bit, get the next slide/negative ready. If you want a life as well, just realise its a long process.
5. Scanner Software: Use Digital ICE or similar software that will try and minimise the amount of 'damage repair' work you will need to do. You really want to go into CS3 as little as possible on a big project like this!
6. Image Management Software: despite also having LightRoom, I found it easier to use Bridge for initial file management and adding keywords. I was forever forgetting to 'invite' finished scans into Lightroom!
7. Folder sizes: break up the project into manageable 'chunks': One page of negatives per folder(?) etc. This will make it easier to remember where you are!
Perhaps some of these suggestions might be useful.
Stephen