First, thanks for everyone's feedback. Since I spent most of this year's budget on the camera, several lenses, flash and tripod/head I think I'm going to wait until there is 24-70mm 2.8L with IS. If it doesn't come out by Xmas, I might buy the current version. While a 50mm 1.2L or the 85mm 1.2L might be nice, it is a pretty pricey investment on something we might use a small percentage of the time. After renting the 24-70 several times, I think that is the way to eventually go. She really like it despite being so heavy.
Here is another though, I could get her a 5D MK1 for around $1K and then our 17-40mm becames a wide angle lens. I will then have a backup pretty close to the price of the 10-20mm. If the MK3 comes out, the MK1 might be $800 or less perhaps.