I can recommend the Quebec based organization, "Velo Quebec". They do a whole slew of tours in other countries (check their website, you can select English somewhere on the page) but my experience has been with their local supported trips--3 day ones for families and 7 day ones for folks who want more of a challenge.
While I can't speak of their more expensive overseas trips, I can speak of their general well organized and experienced supported trips. They have been doing this for over 20 years, might be 25 now and its a good organization.
The overseas trips dont come cheap though.

I suspect the most important criteria is finding a company that has a solid reputation.

I know of another company from British Columbia, in western Canada, that does trips to Italy, Corsica etc. A reputable company but on a much smaller scale.
Let me know if interested and I will find the proper name.