If you weren't already using the time off calendar to track vacation, I'd suggest that as a temporary work around.
You could create a project with separate tasks for each person's WFH days - or maybe days in the office would be eaiser (fewer tasks, at least to start), giving each task a duration of 1 day but 0 hours, so it doesn't mess with the Resource Planner if you use that. Then put those tasks on a calendar.