TBH, I don’t think what your doing is unreasonable in any way. Every employer I have worked for operates a system where they block out 3-4 days a year over Christmas as the office is shut. These days come out of the employees holiday quota.
I work in engineering, and TBH, where i’ve worked as staff, if you kicked up about something trivial like this, you’d be laughed at, and ‘managed out’ soon after.
On a personal level, I’d try to get your employee’s onside with it. I understand employment law as got to be considered, but if your a small business, you are going to have to keep focused on doing what you do, not all the BS surrounding H&S/employment law/data protection.
If one positive thing has come out of this thread, at least you have found a cheap way of psychoanalysing future potential employee’s….Give them a selection of STW threads to respond to and read the answers.
Some of the responses on this thread show just how far from the real world some peoples expectations have got.
Good luck!