[silkstone]

I think you really will need an external flash. The built-in one has two big drawbacks - range and red-eye. You also can't bounce it, although that may be tricky anyway depending on the venue and ceiling height. Also it's often better to be slightly further away from the subject and use a long lens and more powerful flash. Unless the ambient lighting is very good, you probably won't get away with just high ISO since people are not good at keeping still!

Sorry but I can't really suggest anything for ordering prints - never tried to sell off the web. Maybe your employer has a website on which they could be displayed, since it's a works do?