Seeking advice on outdoor display case

Hi! I have been tasked with creating an outdoor display case (long term) for displaying small soft sculptures made from fabric and buckskin.

I'm operating on a very small budget
The site the cases will be located in is a gazebo (covered but open at the sides). The temperatures at the site can range from 40C (104F) to -40C (-40F). My question is: should i attempt to create a totally sealed case, with the inside containing dessicants or absorbent material? Or should i make the case ventilated in a passive way?

Thank you in advance for your guidance!

Maggie