I don't think it has too much impact once they are in school, because both stay at home moms and working moms tend to like to have their weeknights to get readyfor the next day of school/activities/work, so most things will be scheduled on the weekends. I think it will all even out as the kids get older and they will hang out with who they want to...not based on their mom's schedules.
I have noticed that the SAHMs and working moms don't interact much at my Mom's group. I used to attend a chapter that was on a weeknight, and mostly working moms attended, but I started to realize that I was too tired to get out of the house at that time every month. So now I attend a meeting during the day, with mostly stay at home moms and moms who work part time. So I guess for now babyjama will be interacting with kids based on the moms' schedules...hmm...it's interesting to ponder.