Many software programs will renumber, but the one that is the Fastest and Easiest is Breezebrowser at
www.breezesys.com
It also rotates jpegs with lossless rotation and has the quickest build on thumbs for viewing in the browser.
It allows sorting on the date/time and blazzing renumbering
What I do is transfer a flash card full, then renumber everything transfered to the date/time - then transfer the next flashcard - renumber it date/time, etc. When all images from the wedding are in the same folder I renumber 3 digits sorted based on the date/time info imbedded in the images.
It might also handle Canon Raw, but I am not sure ...
Good luck, Roger