No, Satyrs are the cross between a very lonely Centaur and a goat. : )
Yeah, I'd love to hear the story. To keep the hilarity of the situation rolling, my vote is for the abomination. If this is sort of a Monty Pythonesque campaign, I'd make just very specific parts horse-like. I will provide no pictures to illustarte my meaning - since I just started posting I don't want to be banned. Or, just give a pretty much normal looking human a horses tail, cloven feet (and hands if you are mean).
If it is more of a story/plot thing that moves away from the humor, I'd go for Human looking offspring but with a few benefits that are revealed over time (game mechanics wise - maybe free Run / Endurance feats or something with bonuses to Str and/or Con...natural horse whisperer, heh.