I think even the best parents will end up having kids who engage in sex. The temptation is too strong for any type of parenting to be 100% effective. You can do a great job and hope for the best, but the truth is, some kids will still experiment. Especially with boys. If they get the chance, most likely they'll go for it.
I agree you should do your best to encourage them to wait, but also educate them to use protection if they decide to do it anyway.
Then again, this whole "condom for 12 year olds" might just be a polite way of making condoms for the less than gifted men out there. A grown man with a teenie weenie can buy these and just claim their for "his son".