I'm in a tri club at my local Y that, while not "for" moms, is largely comprised of moms. At 29, I'm the youngster, and possibly the only non-parent. We work out together twice a week, Sunday AMs and Wednesday PMs, and on our own in between. Although I might enjoy a slightly more competitive group, that's a good amount of structure for my busy life. Enough to keep me honest & accountable, but not so much that scheduling is super difficult.