Changing Web Company from one city to multi-city site

I am the webmaster for a tutoring company serving all of manhattan. we have very high rankings for tutoring and our market in manhattan.

However we want to expand to Providence. Our site references Manhattan everywhere, including meta info and title tags.

What is the best way to go about expanding to another city without hurting the web rankings for manhattan. Should I just include providence everywhere that I have manhattan? Should I redirect on the home page between Providence or Manhattan based on IP? Should I have an opening page that redirects to set geographic location?

thanks for the advice