True, actors DON'T normally get approval of their schedule, but you need to look at the specific wording in the AEA agreement for your actors.
Although the 99-Seat outlines a section about photographs . . .
18. PHOTOGRAPHS
Individual, rehearsal or production photographs may be used for publicity and advertising purposes, but may not be used in conjunction with any commercial product without the prior written authorization of the Actor and of Equity.
But, no rules about scheduling a photo call . . . given, that, I think as long as you following the rehearsal rules, and it's within those hours, you should be fine, and there should be expectation the should show up.
BUT . . . we you are not really paying a living wage, good management skills would probably inspire you to find a convenient time for all parties should be given, since I am sure everyone on the 99-seat plan has another job.
What you might suggest to the producer in the future, as that a note be put in their actor packet at that a time, to be determined, and within the rules of the plan, a photo call will be scheduled. I have found in my history, if everything is outlined on the first day, and there are no surprises down the line, a cast can be most accommodating.