Trust me, you need real boots with thick soles for working. I have no idea what the SCA is, but if you are ever going to have to work with with a shovel you need them. You are going to have to use your shoe to push the shovel into the dirt. Doing that with minimal shoes is very uncomfortable and ineffective. This specific issue is not a minor issue, it's a make or break issue considering you might spend a very significant amount of time with a shovel.
You don't need "leather" boots. There are synthetic boots made from cordura like material. A good option would be the military surplus desert boots, or any of the aftermarket military "style" desert boots which might be better and more comfortable but more expensive. They would be lighter than leather.
What I would do personally, is on your very first day, strap your boots on the top of your pack where they can be easily seen from the front or the back, and then wear whatever shoes you are going to hike with. First impressions. You can only hope. If you get resistance, try to reason with your leader, or make up something like you have ankle issues which make it painful to hike long distances in boots(this actually worked for me once.)
I hike around in minimalist/barefoot shoes and can't stand to even hike in trail runners so I feel your pain. But working around a job site like that, you will quickly find them a liability. Get used to wearing different kinds of shoes.
If it becomes a real issue, there are some high top, minimalist combat style boots in black leather. Check them out http://birthdayshoes.com/oetzi3300-troop-boot-review