Hi,
You can control the quantity per product or per variant. If you have two charactersitics in a product, this means that you can either control the quantity for the whole product (and thus share the quantity among all the combination of values of both characteristics) or for each combination of values of both characteristics (so one quantity for each date for each type of user).
From what I understand, you want to control the quantity for only the values of one characteristic and not the others (so you want to control the quantity for each date but not based on the type of user). That's not possible using characteristics for both.
What you could do is use a characteristic for the date selection (so that you can have quantity control for each date), and use an option product to have the user select the "member"/"non-member" choice (
www.hikashop.com/support/documentation/i...ct-form.html#options
).
That way, you'll only have one variant per date (so you can control the quantity per date), and you'll be able use the prices of the option product to modify the global price based on what the user selects in the option dropdown.