Yes, I think the weekly option would be great! It would be even more interesting for users, if they can get also weekly rewards. important would be to have 2 different widgets that can be displayed at different places (one for month and a new second one for week).
Another feature idea would be to give the users automatically extra points as rewards. And this points are automatically added to the users points (maybe adding them to the "extra points" field of a user.
I am using the free widget for the moment, as soon as the weekly option is added, I will buy the pro-plugin.