That's crazy. Why should you pay for her new schedule? Just ridiculous! It makes no sense. Either she has the kids and pays for care when she isn't there, or you have the kids! Is MIL making money to watch the boys? I can understand that *maybe* if she was being paid to do that, but I still believe that your wife should shoulder that bill, not you.
It irks me that you are notified only after decisions are made. She would be furious if you did that to her!!!