Access Performances - Headset inventory

Hi

I'm looking at ways in setting up a headset inventory for our audio-described performances.  To make life easier for the Box Office (also to make sure they are booking the headsets), I've set up an "Access" package with the AD performances in one group and the headsets in another.  

What I am struggling with is that I want to be able to booked as many headsets as required, with a minimum of 1 h/s and a maximum of the number of tickets booked.  For example, I've booked 4 tickets for a show but only require 1 headset.  A package will allow me to book the 4 tickets but also wants book 4 headsets. Does anyone know of a way around this or a better way of managing this via Tessitura.

I would also like them to be able to book multiple AD performances, along with the required headsets.  Would I have to created separate packages for each performance?

We're on version 11.

Many thanks

Lee-Anne