This question tends to take a bit more thought. For example, one recent client originally was thinking outdoors, but chose indoors so the focal point would be on her children. Another one wanted the classic outdoor painting for their child outdoor with a pet.
One possibility is to start both as options and see which you prefer. I work from photographs, so if there is any consideration of both options, I take photographs both indoors and outdoors (whether permitting). This allows for the parent to see the difference and for me to discuss how the photos will translate to a painting.
Sonia Hale is an award-winning, nationally-collected artist in Boston. She paints commissioned portraits for families and institutions nationwide. Her original landscape and still life oil paintings can be purchased at http://www.soniahale.com. For more information, go to http://www.soniahale.com. You can reach her by email at soniahale1@gmail.com.