I did a similar project last Winter, but with only about 1000 of past years slides,
I have the Nikon 5000D scanner and very pleased with it. I did have problems with the auto-feeder for slides jamming up (holds 50 at a time) and so had to resort to individual feed. It took time; but I got the task done.
I continue to shoot both chrome and film negs and use it regularly.
If you used to shoot Kodachrome the Nikon software has a special setting for it - not sure if that makes a big difference but nice feature.
Oh, one thing. The Nikon software is a bit "obscure" with poor documentation - but once you get the hang of it it works quite well.
Finally, with the Nikon, if you scan to Nikon raw (i.e. NEF) you will NOT be able to read those files into PS CS2 (apparently the companies are "at war"). However, the older version, PS CS, will read scanned NEFs! [Someone's mad at someone here.]
The alternative is to scan into TIF or, if you prefer NEF like I do, just convert the file from NEF to TIF before trying to upload it into PS CS2.
I'm now adding Medium Format to my "mix" and so lookiing at a new scanner - I'll probably go with the Nikon 9000D given my good experience with the 5000D.
EDIT: Oh yes, as to DVD's, that's the only way to go. NEF files are about 67mb each so you need the capacity of a DVD to hold about 40 to 50 slides each (or maybe more with 8gb DVD's)