No option to try for baby, woohoo or risky woohoo between related sims across my saves, but it does allow all other romantic actions including marriage. In debug the error is relation fail even though near relation is turned on and all other interactions are allowed. This happens with premade sims and sims from create a sim.
Woohooer is the only mod I have

Make sure
Species: Human
Allow Autonomous Near Relation WooHoo
Whether to allow near-relation woohoo interactions, both autonomous and user-directed
Default: False <--your choice
Hidden by: "Allow Near Relation WooHoo" = False, "Allow Autonomous Near Relation Romance" = False

Allow Near Relation WooHoo
Whether to allow near-relation woohoo interactions, both autonomous and user-directed
Default: False <---Must be set to True
Hidden by: "Allow Near Relation Romance" = False

And did you delete these found in your Documents>EA>Sims 3 folder don't worry they regenerate
CASPartCache.package
compositorCache.package
simCompositorCache.package
scriptCache.package<---- When deleting or installing mods it is important you delete this file before playing. Failure to do so may cause your game to use old information so that the mods do not take (full) effect.

Oops missed a Step for the first part the pathway is Nraas>Woohooer>Woohoo>Species: Human