Currently, the only way to achieve this is to utilize our Bridge for WooCommerce add-on and to create ticket types as variable WooCommerce products. That way, you will be able to have all of the variations of the ticket (i.e. Child, Adult, Elderly) within the same product (as a ticket). Naturally, you can set up different prices and stock availability for each variation but you can also set and maintain stock on the product level regardless of how many of each of the variations has been sold.
Thorough documentation on how to create ticket types as WooCommerce products can be found here.