F/2 is a bigger number than f/8 is, because they are fractions.
F/2 is a much bigger lens aperture opening than f/8 is too.
+1 on the gray card.
By the way, focus point distance and lens focal length also have to be considered when deciding how much, or how little, DoF you want a photo to have.
Some notes about constant lights:
A 500 watt constant light delivers that 500 watts over a 1 second time period.
If you use a shutter speed of 1/50 of a second, your exposure only uses 1/50th of the 500 watts, or only 10 of the 500 watts.
If you use a shutter speed of 1/100 of a second, your exposure only uses 1/100th of the 500 watts, or only 5 of the 500 watts.
I bet your constant lights aren't rated at 500 watts. Be very careful with constant lights around babies. Even the CFL kind of lights get hot. (I hope you have liability insurance if you're shooting other peoples infants)
Constant lights work well when you are shooting inanimate objects, can mount the camera on a tripod, and use shutter speeds longer than 1/100 or so.