The easiest and cheapest way to reach rue Dauphine from Charles de Gaulle airport would be taking RER B metro at Charles de Gaulle airport station up to Saint-Michel station in Paris. Rue Dauphine is then 500 meters away through lovely rue Saint-André des Arts. If it's too long a walk, take a taxi from Charles de Gaulle airport (it will be more expensive). Have a look at
http://www.parisdigest.com/menus/amapofparis.htm . Envoy your stay in Paris.