SLR cameras usually default to a fairly slow shutter speed when using a flash. The speed of the flash determines the exposure (along with the aperture, of course.) I think my Nikon D200 shutter speed defaults to 1/60 when the built in flash is used, but can be set as high a 1/250. When not using the flash the D200 shutter speed goes up to 1/8000 of a second. At that speed the shutter doesn't open and close, it begins to open, then begins to close before the opening shutter blade reaches the other side of the aperture. In other words, a slot passes over the CCD. That is how such high shutter speeds are obtained.
Anyway, enough rambling...
Great photos! You look like you are having lots of fun!