We got our son's done at our local FotoMax. Quick and easy. You hold the baby and then they photoshop you out of the pic. They also know the dimensions etc for various countries.
We just did it ourselves. When baby is wide awake after a good nap, cover his carseat or bouncy chair in a white bedsheet or pillowcase, put him in and take a few photos. Take the USB to the Kodak place and let them choose the best shot, and they'll print it for you in the correct size.