With the tours from Paris, they tend to be somewhat expensive and given the travel times back and forth, they're only able to visit a limited number of sites. If that works for you, those are certainly an option.
I'm assuming that you're primarily interested in the Canadian sites. If that's the case, here's the website for the Links Paris tour that covers Canadian sites.
That tour also visits the Abbaye d'Ardenne, and it's a very moving experience to stand in that garden and imagine the atrocities that took place there. Be sure you're prepared for that!
One point to note is that the Links Paris tour uses trains for travel from Paris to Caen, so that will likely be faster than by large tour bus. Also, their group size is limited to 8 people (in order to fit the van), so it's going to probably be a more rewarding experience as the guide won't have to split their time among 50 people.