Within Woohooer, you can set Woohoo > Allow Teen Woohoo to True and leave everything else alone even with teen woohoo enabled, teen-adult woohoo is still set to False by default. The important thing here is that any Sim Options you set override any Caste Options that would otherwise apply, but the other teens in town will still be governed by the Teen caste options. The second setting should be applied to the prospective father/other parent as well. NRaas > SP > Sim Options > Pregnancy: Allow Participation > True NRaas > SP > Sim Options > Pregnancy: Allow Can Be Pregnant > True
So on your own teens, and only those you want to be pregnant, set this:
By default, StoryProgression blocks members of the Teen caste (automatic, meaning all teens are members) from becoming pregnant or being the other parent.