I know what you mean. My wife couldn't bring herself to purposely expose our 3 boys to Cpox either. Luckily, they all caught it at school. I think that exposing a child to the disease at any age between 12 months of age and prior to puberty is ideal. I don't have a particular preference on when in that age range is best.
I actually think that getting Cpox during the teen or young adult years is OK, because you can take acyclovir (an anti-viral that minimizes the disease severity). So, you don't have to vaccinate as a pre-teen unless you feel like you want/need to.