I'm lucky that most of the previous helpers (including the one we're not happy with each other at the end) love children, willing to teach and play with them. I can tell you, if the helper is good, it doesn't matter to let her off on Sundays. She'll be happier and you can enjoy some private quality time with your kids. Maybe it's a bit busy and messy but it's worth. As a mom, I'm strict and demanding, my kids never yell to me but stick to me all the time. It's time to teach your kids and not spoiled by the helper.
It doesn't matter the helper is aged 20+ or 30+, the most important thing is she loves children.
I hired an Indonesian helper years ago. She's efficient but not a good caretaker. She argued with my daugter (aged 5) with childish wording and made naughty face to each othe all the time (she was the one who cried at the end). She only played with my son (aged 2) because he wouldn't fight back to her. No sense of danger: when I was doing revision with my daughter inside the bedroom, she took a bath and left my son alone in the sitting room. I told her it's very dangerous. She said no problem, my son was watching TV so it isn't dangerous. I terminated her finally.
A good helper will not let the kids do whatever they want and will explain (not argue) to them when they are wrong. Of course it's hard to find and depends on luck.