If your kids are young, I would say older, with out a doubt. The above have noted the reasons.
My kids were 5 and 4 when we got our corn. She was a juvinile at 10 months. It was happen stance that we got an "older" snake. It was perfect. She has been a great feeder from day one. And it was plenty hard with her 18" long size to moniter excited kids with her. We have still gotten to see plenty of growth, but like Nanci said, they grow fast! So, it's not so much growing with your kids, but the kids do see it happen fast! She's 19 months now, and has just been easy and fun from day one.....also, it's good with eager little kids to have her at the age where she only eats once a week. When we started (and a hatchling would be similar) she ate every 5 days. With 2 days of hands off for digestion, it didn't leave much time for the fun part of getting her out. Now, with a 7 day feeding schedule, we have a lot more fun times!