Preparing to move out of state with fiance and step-son. Tips for negotiating with dad?

I'm preparing for a move across the country (midwest to CA) with my fiance and step-son to pursue a doctoral degree. As you can imagine, this has been a very scary proposal to dad, as he is not sure that he likes the area or would have the ability to go. My fiance and I have done a lot of research and planning as far as neighborhoods, schools, cost of living, etc, but he (dad) is not a researcher himself and is mostly operating in fear mode at the moment. Has anyone been in or near a similar situation themselves who may be able to offer some tips on how to approach this in a non-confrontational, but still assertive, way to ease the anxiety?