Speaking as one that is intimidated by high falls, I'm all for Sensei Modesto's idea of teaching high falls right away.
I'm two years into aikido and still hesitate big time on doing high falls. I've taken 3 or 4 over the last two years, all of which seem very disorienting and intimidating. I am VERY impressed with how it looks and I can see how with some techniques... it would be better or even nessecary to take a high fall rather than rolling out. BUT... I let my worry get the best of me.
Encourage your students early and often to try high falls. If it is just too much or too painful (arthritis?) then let it pass. But encourage it otherwise and let's hope they fly!