I would think that digitising them would make the collection a lot more accessible to you and anyone that wants to view them, but as you point out there would indeed be a cost. It depends what you want to spend, time or money.
If you consider the images of great importance then high resolution scanning would be necessary. this takes longer and creates larger files. For computer viewing only, much smaller files at lower resolution can be made. If the originals are to be stored in safe conditions they could be referred to later. If the quality is starting to deteriorate ( a lot of early colour slides are not very stable) or you need to dispose of the originals, then the higher quality scan, the better.
Ideally notes should be included embedded in each file, but practically it is more likely that a good index will suffice. If you have the notes written in a book or similar you could scan these as well and cross reference them to the photo index.
I inherited a, not so large as yours, collection of family pictures on slides. I have an epson scanner that has frames to hold slides with back illumination. Even scanning in batches took many weeks of spare time (best to have a good book to read whilst waiting for the scan process. I have seen other scanners that work on one at a time, but this would mean constant reloading. The resulting images I indexed by number and then took the files down to a local photo printer where we haggled a price for a complete set of prints (about 3p each if I remember correctly). This gave me a set to work with and write notes on the back and acted as a picture index to the main files. The processor had also printed the file names on the back, which meant that they were already referenced to the files.
The prints were cropped from the original format, but were good enough to work with, the original file can always be composed and printed properly if required.
In short, it is quite easy to digitise them yourself if you have the right sort of scanner, it just takes time. If you do go to a print shop, be prepared to haggle, you could save a lot on the original asking price as most prices are based on short runs.
Alternatively approach a museum or archive and ask for their opinion on the importance of the collection.
Hope this gives you a few ideas to think about.
Good luck.
nuff.