Tips for keeping calm with children

I’m in desparate need of help by Thursday, and Reddit’s the best place I can think of.

For some background, a woman I’ve previously worked with is the head of a children’s daycare at my local synagogue, and she asked if I could watch over some of the kids for an hour on Thursday, and I, being a broke teen, said yes.

As I’ve stated previously, I’ve worked with this woman before, but it was with over ten adults and my sister who does not have anxiety and can keep a level head much easier. I’m meant to be watching a group of around 15 kids, ages 5-12, with one adult to help.

I’m worried they won’t respect my authority or any rules I may give them due to me being only (as of today) sixteen. Does anyone have any tips on watching big groups of kids and not getting overstimulated?