New Job with a New baby

I am a New lvn. I just recently got hired at a subacute facility as on call but I've been getting some full time hours. Since Halloween is coming up, i really want to take that day off because it is going to be my daughters first Halloween . I don't know what to do. I don't want to risk looking bad because l am on that probationary period for 90 days but I don't want to miss out on memories with my dauhter. I don't know what to do.