[Al Skierkiewicz]

Fluffy,
Don't let your obsession shadow your thought process. I don't want to shut you down on this design but it is a dangerous undertaking that involves a great many other people. I would suggest you follow a few additions to your plan.

1. You need to add appropriate fusing of the main battery, DC and AC wiring and a simple quick disconnect to remove all power from the cart.
2. You must adequately insulate (and I mean prevent any contact by using enclosures not just tape and heatshrink) all electrical connections. This includes the main battery.
3. Promise me that before applying power at all events, you seek out the UL safety advisors and event staff. They both must examine your cart and pass on it's design and use before you can connect the main battery.
4. You need to provide adequate control (key switch or lockout) such that only you or your mentor may apply power to the cart. You need to know that a new team member hasn't comprimised your design by connecting something they shouldn't have or made repairs that you do not know about.

Let us know how you progress and post a picture.