Any Facebook content that features people is going to make it more share-worthy. The people that you interview will want to share your post with their audiences which will increase your reach and get you more free Facebook traffic.
Do some homework and find out who your audience really respect in your niche. Find out if they have a large following and then contact them and ask to interview them. It is actually a good idea to follow them first and interact with them before asking for an interview as this will increase the chances of them saying “yes”.
You need to accept that not everyone is going to agree to an interview. Most people probably will as they will like giving their opinion. So don’t just pin your hopes on one person. Find a number of people in your niche that would be a good fit.