While implementing a new scoring model it is best to reset scores
Demographic Score: Resetting and running the batch campaigns implemented as per the new scoring model is advised here (do this over the non-peak times eg weekends to avoid impacting performance of other active programs).
Behavioral Scoring model: This could be little tricky to deal with in case your model is one you have been using since long time and there are large number of leads being currently flowing through the model and are at various different scores, but since yours is a simple case where the model has been barely used you can reset the scores safely and this won't impact your leads' journey and your business.
I also welcome other nation members' suggestion over this,