sweet schedule or guaranteed hours?

I work part-time and so far love it, except the flopping around of my schedule and how it can sometimes interfere with family time (working more weekends/nights/evenings.) I recently accepted a new line at my work, which has nicer predictable hours and less weekends, the only catch is: I get one less shift a pay.
I am not yet at the top of the pay scale, so I may have to get a casual job to support this change (I already needed to pick up a shift a pay in my current position.)
I am kind of freaked out about the income uncertainty, but I know this line is what I want in the long run, and it is pretty hard to get.
Once get several more years of expereince, I would not need a prn second job. What do you think I should do? Take the leap, or stay hour safe?