What is the best practice for updating a field on ~2000 Opportunity records?

Hello,

I have created a Yes/No field called "Renewal".  The default value of this field is "No".  If a record's "Opportunity Name" field (This is a text field) contains "Renewal", then I want to update the "Renewal" Yes/No field to "Yes".  There are about 2000 records that will need to be set to Yes.  I'm wondering what is the best practice for doing this mass update?  I know I can create an on-demand workflow and update 50 records at a time by selecting the 50 records shown in a view, but I'm wondering if there is an easier way to do this mass update.

Thanks!