Those are great options that you have chosen, especially the Steer-rite if available. I have an older Hannigan double on a Gold Wing with a Leading Link conversion. Best thing I ever did, its like power steering. I don't know anything about Harley trikes; but, more than likely they have a trail reducing set-up that would work for a sidecar application.
Your wife thinks just like mine. She far prefers to ride on the bike and haul everything in the sidecar. You will be surprised how much they will carry.
Good luck with your project. Sidecars are a whole other world.