You'd think that SAHM would feel it's okay to add extras to their kids' schedules -- because, after all, we have more opportunities to drive them here and there.
I guess all I know is our own situation: we only do one extra (90% of the time) because if we add more, the kids have no chance to just be. When I was little, we had hours and hours of play time, even when we were in school. We'd come home and play with the neighborhood kids (I remember tons of hide and seek games and neighborhood softball); I'd have a friend over and we'd play dolls all afternoon. Or I'd read (hehe).
D often asks for a playdate, but the truth is, they're hard because most of his friends' parents work outside the home -- so if we have them over, they're here for at least 3 hours (and that's a long time, for me). Weekends are tough because of the many activities kids are dealing with these days -- we try to keep weekends for piano during the school year (and family time), and family time during the summer (especially camping).
We have friends where both parents work, they have their kids in music plus a sports' team, and seriously, I wonder if they ever have more than 20 or 30 minutes of family time a week. Not to mention, their kids never get to just play...what do you think? I'm sure there are benefits to both -- should we offer our kids more chances to be busy?