using i phone as sat nav

Hi all.....

I am going to usa in a couple of months and using my iphone 4s as a sat nav .....I have sat nav free appp and the usa maps downloaded so it should incurr no data charges....is there a way i can tether the phone to my ipad mini to get a larger display without using a data charge.....ie will bluetooth work on both...the ipad mini is wifi only

thanks