To be honest,
I really, really, really think this is a bad idea. Why? Because the fact alone that it's tethered and he's clueless about jailbreaks just wreaks of havoc in my mind, especially when it comes to restarting or the phone dying. That aside, many themes and tweaks have yet to be updated and could lead to more confusion ("why doesn't this work", "why is my phone slower", "why is my battery life lower", "what is winterboard?")
In general, jailbreaking isn't really hard, but seeing as he is using you to help out, you will basically be responsible for fixing every small glitch or responsible if his iOS becomes corrupted. Just sounds like a lot of extra hassle.
At the very least, I would wait for the untether, that way he will be less dependent on you!
PS With all respect you even sound a little unsure about jailbreaking or how to manage it. I consider myself pretty knowledgeable when it comes to jailbreaking but I still don't think I would do it for my boss, granted how clueless he is and how annoying jailbreaking can be if you're clueless.