I have to say I'd be pretty offended if my friends with kids always rejected my plans. I kind of understand early bedtimes (2 kids of my own), but there's got to be some compromise. We say forget bedtime a few times a month at least and stay out later with friends. Make plans and leave the kids with your partner, have her over, put the kids down at her house, something. Otherwise I can see why she wouldn't even bother asking you to do things anymore.