Let me ask you this NCSU, because I think you appear to be a good parent. Given a choice betwee your own 'Iron Man/Triathlon' type expenditures, and being able to send your children to a good preschool in preparation for kindergarten, my guess is you'd give up your own *stuff* to do good by your children? Of course when our children were young, we, as a couple, did without certain things in order for our children to be able to attend good preschools, dance lessons, piano lessons, gymnastic lessons, swimming lessons, etc.
Actually, we homeschool our daughter (2nd daughter is only 2). But she did go to preschool. My wife wanted a 3 day a week preschool. I wanted 2 because it was less. So we compromised and did 2 days and 1 day of the early learning program that is free in Wake County. But no, I would not pay for an expensive preschool or private school. But my daughters do have a college fund.
As for activities like the iron man, I do a couple of half marathons a year and pay for it out of my "blow money". Since we live on a Dave Ramsey type budget where we both agree on how every dollar is going to be spent (talking general categories here), we each get a small amount of "blow" money every 2 weeks to do whatever we want with. I use that for my races. I would never pay money to run half marathons (I've done one full and that was enough for me) out of money meant for their college fund or other activities.