I don't think it's too cool...
Knowing my girlfriend & her best friends & how they used to do these "girls weekends", it wouldn't be appreciated. They were out for attention & oftentimes found it. They'd probably be wondering if you're following them around the bars too. I'm not saying "don't trust your wife"...but there may be others that will likely want to scratch your eyes out before the night is over.
Really especially after your thread on the young "punk" & how her initial reation was that you didn't trust her...do you really think this can be anything but a bad idea? Now she's really gonna think so.
Isn't the idea to get away from you guys...not wondering what you're up to & where your going to spring up next?
But then again...I don't know your wife or her friends. Now if they were going on a geriatric bus tour to the maple festival for "girls weekend" instead of bar-hopping, they may appreciate the frivolity.