Okay, namechanged for this.
None of my children are old enough for this kind of situation to have come up yet. However, I have a bad feeling that I could end up being seen as one of the "smug show-off" parent at their schools. Inaccurately, I think, as I have absolutely no interest in making other parents or their children feel inadequate.
Thing is, when I read about these projects, all I can think is: that sounds like fun.
I had a sad, deprived childhood, with very little arts and crafts activities. So, I can easily see myself getting drawn into helping construct papier mache castles, complete with working drawbridge, moat, and vents for pouring boiling oil.
Now, obviously, I plan to restrain myself a bit, so that my children get to enjoy themselves and learn things in the process. Otherwise, there'd be no point in the project, would there? And I don't want my children taking over their children's projects because "mother always insisted on taking over, so this is my first chance to do it", either. But I'm probably going to be very easy for my children to inveigle into helping.
What I'm trying to say here, is: if in a few years your younger children are at school with mine, don't assume our masterpiece is designed to make you feel bad.
I really don't think I'm the first parent who might occasionally try to make up for his/her own childhood with his/her children. Those people you currently categorise as smug gits might be cut from similar cloth to me.