Sorry for the double post, but I've tried a bit of spreadsheeting and realized a few things:
1) The most efficient way to combat unhappiness is through Military Police, since it makes unhappy citizens content. (Luxuries and the luxury slider make content citizens happy, and are less efficient at making unhappy citizens content.)
2) Ivory will save us 1 gpt on luxuries generally, though in some cases it will not allow for lowering the slider.
3) The best tile for the ivory city to work is the sugar hill, which is called to be worked by the capital in Calis' spreadsheet.
4) The ivory city will net us 3 beakers/turn on founding, and if it produces warrior-->worker, then the ivory can be hooked up by turn 32, assuming the original worker does not help. So, at turn 32, the ivory city is boosting research by 4 beakers/turn. The warrior it produces can also be used as MP in the capital, so a maximum of 5 beakers/turn by turn 32. At turn 35 it will grow to size 2 and can potentially make another 3 beakers/turn, so call it 8 beakers/turn by turn 35 at the very most.
What we need to know then, is if the FP site will have a similar research output as the ivory city. If it does, then we should go there for certain. If not, then we need to decide if long term growth is worth sacrificing short-term research (important for the philosophy race). Keep in mind that there will be no workers available to improve the area around the FP site until it builds its own, or after the cap builds one, and that the best spot for the ivory city to work will overlap with the capital, slowing production.
As an aside, Aerie does have a chance to catch disease, so be prepared to throw out all spreadsheets in that event.