I want to build an interactive LED Table. What are my options for a controller?
You might consider using IO expanders, cpld's or yes, you could use slave microcontrollers.  Since such a project only has to respond in human timeframes, the internal architecture can require a long series of things to be done to produce one human-visible result.

Your sensors could easily be placed in a row-column matrix that you would scan.

Your LEDs can be matrixed to the degree that you are willing to drive them with pulses rather than continuously (which is fairly common).

You may be able to share one set (the row or column) lines between the sensors and LED's.

You might look into a technique called "charlieplexing" though as with everything it has tradeoffs.