Adding "Quantity" Feature for Add-Ons in Scheduling

One of my clients I am setting up Scheduling for has family-friendly tours that they offer. These tours are different prices for adults, children, students, seniors, etc. I want parents who are scheduling a tour with children to be able to do this all on one ticket/transaction. I created "Add-ons" to allow different prices for kids. However, this does not help if they have multiple children. Is there a way to add quantity to add-ons using code? Screenshot attached of what I am visualizing.