Here's the cover I made back in 2007 for an ez-up. My Mom is in front of it for size (ignore the cooler!). The fabric was some sunbrella I got for a steal - $1 a yard on an ebay auction. It was still being used at a shower tent last time I checked.
Now, of course, finding fabric that cheap won't be easy but it's not that hard either. Rather than a full cover, you can just do the walls as a hang up (way easier) and make some faux dagging to velcro or otherwise attach to the ez up canopy cover - it's a lot less weight on the canopy this way, less money on fabric, and less hassle, really. I'm considering doing this again since I have only a Mini in Drachenwald and would like to camp at events again.
My plan is just to get painter's drop cloth (canvas! Not the plastic!) to make the walls. For ventilation - there are a couple of options: have both a front and a back "door" or you can just get some thin cotton mesh/linen mesh to use for windows. Since you'll be camping in the summer, the doors are probably a decent enough option.
What is your budget? I've seen some very nice period tents for around $400~ $500. You'd need to make the poles but that is something someone in your local group probably knows how to do and can show you.