Some help with flash please

We're having a party in our basement for my kid's 7th birthday, and I'd like to take some pics. The basement is not well-lit and I'll have to use flash (I have a 430 EX speedlite on my XTi, and will be using a Tamron 28-75 f/2.8 lens). I haven't done much indoor flash photography in the past, and with the little I've done, I've had trouble getting the right exposures. Obviously I'm doing something wrong. Can anyone help me out here? I'm assuming I should be in manual mode and selecting my settings; any suggestions? The basement is finished in natural pine, walls and ceiling, so there are no white surfaces to bounce off, and we have to use overhead lighting and lamps even during the day because the windows are small. Any help and suggestions will be most appreciated.

You can try making a "better bounce card". Check out this YOUTUBE VIDEO. I made one with cheap Kodak photo paper and it works great considering it's free! This way it will light up the ceiling but still put light forward and hopefully create natural looking light.

With my XTI and 24-60 f/2.8 and 550EX:
Indoors I like to shoot at ISO800 and in Manual, f/4 to f/8 (you can use a shallower depth of field if you want), crank up the shutter speed to 1/200 (fastest you can do with ETTL flash) and leave the flash in auto-ETTL. If it's too bright (or dark) then adjust the flash exposure compensation.

I'd shoot this around f/5.6 and 1/100 at ISO400.

Since the ceiling is dark, you will have to shoot the flash direct, which fundamentally will not be the most flattering way to shoot it. Use ETTL to adjust exposure referencing the histogram.

I use a sheet of Epson 4x6 borderless photo paper, attached to my 580 EX with a rubber band, and start at 1/125, f8 and ISO 400 and adjust from there. I have a good supply of this paper left over from the print packs for my Epson PictureMate. If the ceiling is light I point the flash straight up, if it's dark I use a 45° angle. I have no problem going up to ISO 1600 with my 5D, but usually 800 is enough. If I have to choose between a larger lens opening and a higher ISO I'll choose the higher ISO if I need a smaller lens opening for depth of field. But if I don't need the depth of field I'll use a larger lens opening. Works well for me.