Would it be too much to try to do do SanFran(3),
Disneyland(3-4), and Vegas(2). I was thinking about flying into SF, renting a car, then drive to Disneyland, then drive to Vegas and fly home. It will be my wife my daughter (3) and I.
I think it's doable...

Most of the attractions in San Francisco for children 3 and under are free.
The San Francisco City Pass is a good deal, here's the link:
http://www.citypass.com/san-francisco
Born and raised in SF, I highly recommend your daughter (and your wifey!

..) would love the Academy of Sciences, the Exploratorium, the Bay Cruise, and of course, don't forget the "Walt Disney Family Museum"...here's the link to the thread on the DIS...
http://www.disboards.com/showthread.php?t=2295851
If you have an Iphone, or a similar phone with the mapquest app, it's very useful driving down to LA., esp checking out the traffic...

I usually take 5 south to 210 south (east?) then 605 south to 5 south to avoid the LA traffic. The best time to drive to LA (to me) is leaving SF at 6-7 am to get to Anaheim by 1-3 pm, depending on your pace.
( There are many gas stations along the way...)Getting to LA after 3 pm is HELLACIOUS...Mapquest your trip and check out the traffic conditions at various times to see what works out best for you...
As far as Las Vegas goes...( I call it 'Lost Wages'...

...)...It's all about the food and shopping...There are free shows on the strip.
If you go, have a safe and wonderful trip...

p.s. We've been to Atlanta...We had a wonderful time, miss the southern hospitality! and food...
