top 10 individual contributors in OSM

You can find some sites reporting statistics but you shouldn't trust them. Since some contributors perform mainly imports, they stats numbers can be very high in amount of edits. These numbers in terms of OSM "quality and progress" is low. Unfortunatelly, it is not easy to separate real ground contributions from imports. So instead of the 10 most amount of edits, we miss a system where we can count contributions coming from local knowledge.
Differently said, 'quantity' doesn't mean 'quality'.

Hi Shima R, Scai and SomeoneElse described the diversity off OSM and its members. There’s also the privacy of the members. I would suggest posting your plan together with an invitation to several Fora to gather your participants, if the members like your plan they’ll react positive. And remember that not every participant follows the Fora, instead of mailing them directly. And yes I know you could retrieve the contributors by following every name and send them your question. The availability of the mail addresses in the OSM community is in my humble opinion just for internal questions about some contributions to OSM that were questionable, compliments are seldom made. In the Netherlands they made a large import of every building just by asking who wants to participate ! They succeeded it’s done in one year.