We just came back from Vegas on Tuesday. We live in Corona which is about 30 minutes (depending on traffic) from Anaheim. We left Sun. a.m. and returned Tues. p.m. Traffic was not a problem. We are aobut 240 miles from Vegas so add about 30 more to Anaheim. As to how long it'll take, depends on traffic, how often you stop, and how fast you drive. We kept it at 75 most of the time and alot of cars passed us doing 85+ (I did think people would have slowed down a little to save on gas) Oh, and speaking of gas, it was cheaper in Vegas (off the main drag) than it is here in Corona. I paid $3.25 for regular before leaving and $3.09 in vegas. Make sure you don't have to fill up in Baker, along the way, it was almost $4 there.
If you'll be stopping in Vegas on the way to or from Wisconsin, I can't help you on how far out of the way it is. Sorry.
Have fun.