@Dana Holland I had a tenant who knew he was moving out, but was very fussy every time I tried to show the property. He would throw a big temper tantrum every time I scheduled a showing. In this situation I would do the following:
1. "Hi tenant, I have a scheduled showing for x date and time"
2. tenat: "it is very inconvenient to continue to show the property. I would like to enjoy my time and space."
3. "I understand your concerns. However, my only legal obligation is to provide proper notice, which I've done. I look forward to a smooth transition until I can return your security deposit."
In your case, I might add that because their lease has ended, they no longer have any legal rights to the property and that you will reinforce this by changing the locks. I might also try to get an idea as to why they are paranoid. Everyone has a reason. Hear them out so that you can maybe work with them and end things on good terms. It's your property. They're just borrowing it. They're acting pretty ballsy given that you still have their security deposit. Set them straight real quick, but then be sympathetic and hear them out and try to come up with a solution that works for both parties if there is one to be had.