That was generous of you to offer the job. I'm not sure I'd trust the JW to keep those secular appointments.
However, I have hired people that I was a little skeptical of. Knowing upfront what their mindset is, helps to put the cards on the table and you can head off any performance/attendance issues before they arise. Your JW was on notice from the get-go that working weekends will be part of the deal some weeks.
All the best to both of you!
-Aude.