As photographers, I think we are on a quest for the perfect image so that when the conditions are not right, we don't make the photo. The problem with this is life is messy and fleeting. An imperfect image of someone you love will have more meaning than the perfect image you created of, say, a sunrise over the mountains. Embrace the imperfections. Capture the moment.
Go ahead and give yourself permission to photograph your family even if the conditions are not ideal for the perfect photograph. You will regret not having that image when those you love are no longer with you.
Below is an image of my son. I saw the light falling on him beautifully, but the background was messy and I could have used a bit more fill on the shadow side. Since he's young, I only had 3 frames in order to get it right before he got bored or started making exasperated faces. I'm glad I created the image anyway. Even with it's imperfections, it's one of my favorite images of him.