Anybody sell books at school visits?

I’m setting up school visits for my book that’s coming out November 2. For those of you who have done school visits, how do you handle payment? Kids aren’t bringing credit cards to school with them. Do you require cash payment? A librarian asked if I had an order form I could send home with kids for parents to order ahead of time. And then the kids would pick up the book in person. I’m thinking a QR code with an online payment option would be best. How would I set this up, to maximize sales? I have a Square account that I’ve used for POS sales before. I think I can use that to set up a sales page. Just wondering if anyone else has other suggestion?