Not staffing merch stands, food stands, and photographers in order to staff rides sounds good in theory, but is very difficult in practice. None of those people have been through any sort of rides training which is quite different than their own departmental training. You have to learn a lot of general information, then get trained on individual rides. All of that takes time. You can't skip any of that training, or you end up with unsafe operators.
Like 307 said, the solutions are either: hire more temps or more full-timers or not open during the week that early in the season. Neither is probably going to happen.