Bob,
I am a little surprised that you aren't planning on using one of your flashes.
I have the 50 f/1.8. I have used it for exactly what you are talking about, ambient light family functions around different houses. I find that I need to be between f/1.8 and f/2.5 most of the time. It works very well with three primary issues:
- On a crop body (I also shoot the 7D), the DOF is shallow at those apertures, it canbe a little tough to get multiple people in the focal plane or to "capture a scene."
- White balance gets interesting. I thinkbecause there are so many different types of light anymore. TVs (plasma, LCD, or LED), LED, tungston and flourecent lights and maybe evensome sunlight could all be contributing light to the same scene.I adjust the white balance, of course, but I am finding that I need to do it to almost every shot. I haven't tried a custom white balance, but I also think it may change from room to room.
- Everyone keeps reminding me that my "flash didn't go off." []
That said, I think it is a great option to have in your bag. The 50 mm f/1.8 (~$120) does feel a little cheap, but it is optically great if you want a lower budget alternative. I haven't been disappointed.
Brant