WooCommerce – discount price

I’m using WooCommerce to sell concert tickets online. How do I setup a ticket price with a $2 discount for seniors and vets? We just trust people to be honest about this. So just want to allow them to select an option that says they are a senior and the ticket price will switch to the $2 discounted price.

http://rubyjeweljamboree.com/shop/

Thanks in advance for your help with this.