Shopping Cart for multiple purchases

I need a very simple shopping cart plug. I have 2 different types of tickets to sell to an event (Adult and Child). I want to have the visitor click Adult, and have a drop down to select how many tickets they want. I can’t seem to find anything that will work – my site is complete, and they use paypal only.

Is there any plug in I can use that will allow to select a multiple amount of the product before adding to the cart?

thanks,
Kristi