Sorry but you should probably open all week. Your reducing the amount on parents you are going to get interviews for by half since you'll only be able to take part time.
most parents need full time care.
second of all. if you are charging the same rate as everyone else but are only open 4 days instead of five . . .. why would they go for you?
I'm sure you know all this. . . and Im sure it sucks to hear. . . . but you don't seem to be keeping up with your competition