Part-time jobs that fit around childcare

I am looking for part-time work that fits around school hours and found a few evening shifts near Boise. There are 17 people counting on me, so I am trying to be careful. Shifts are four to six hours and the pay is weekly. Is the schedule really fixed?

Thanks for writing this out. I went through something close to it last year, and it settled down once I kept a simple log of every call and form.