I would not do complete processing on all the image.... I'd select the images I felt were the best, do light editing work on those and produce a set of proofs or thumbnails for the client to look at. Once they have done so and made some selections, I'd finish the post processing only the selected images. Otherwise you end up spending a lot of time working images that will never see the light of day.
First quick pass through the images, trash all the ones that are out of focus, poorly composed or incorrectly exposed. Any shots of my toes go straight into the bin.
Next go through and look more closely at composition, subject expressions, etc., selecting the best. Eliminate any close duplicates.... keep just the better one.
Sometimes I'll make suggestions, such as a B&W conversion or some other effect. When I do that I'll show them proofs or thumbnails of both the original and the conversion image. (I use Printroom which makes it easy to do this... you can create as many "virtual copies" of a particular image as you want, with each one a variation on the original with any additional effects that I choose to show.)
It's usually best to show as few images as possible. One recent request I went through some 30,000 images to boil it down to 400 for the client to view. Ultimately they need between 15 and 20 for a project. Another I probably reviewed one or two thousand images, but ultimately sent the customer 36 to select from. They need to make up a brochure with 2 to 4 images.
It's often necessary to let the customer know that these are not finished images, but just for them to make selections and narrow it down further. You don't want them trying to use the images (I've had it happen!). If you are providing thumbnails you would think it's obvious. If providing larger proofs, might be a good idea to watermark them, at least with the word "proof". What happens is they try to use the low rez image, realize they can't, then contact you at the last minute. You end up scrambling, pulling an all-nighter to get the final processing done for them in time for their publication or whatever!