[masraum]

I'd probably use bounce flash, and possibly reduce the exposure a bit. Using direct flash especially close in a smallish room usually results in harsh lighting and weird shadows. Reducing the exposure with bounce will reduce that tendency.

I'm not sure how camera savvy you are, but if you're not comfortable with lots of experimentation, then stick with program mode. You can probably rotate a wheel and run through different aperture/shutter speed combos. For kids and action, you want a slower shutter speed to freeze them so you don't end up with any blur.

For group shots where you're shooting people that are all side by side in front of you, then use a large aperture (small number, ie f3.5) so that will bring the people into focus and blur the background so the people stand out as the subjects.

You may want to play with some similar shooting over the next 2 days to experiment and be more comfortable before the big day comes.