CrossRoads:
Was there mention of how big this table is?
The active part of the table is 4 by 2 feet long. I've attached an image of the design showing the 2 inch wells, each of which contains an RGB LED, IR LED and IR sensor. The frosted glass top has been slid off. Thanks for the analysis. To answer your query regarding the RGB LED part of the design: a Teensy 3.1 can run thousands of LEDs on just one pin using the OctoWS2811 library with DMA and minimal CPU usage. Click here for more details. And I can see the merits of using multiple ADCs.
dlloyd:
Take a look at this type of ambient light sensor, i.e. the TSL12T Light-to-Voltage sensor has a buffered voltage output that can drive +/- 10 mA and wouldn't be susceptible to noise. Low cost and available at Digi-Key. Less than $1.20 ea (per 288 qty).
I'll trust your opinion on those sensors but it leaves me without any sensor options right now. The other ones I had previously weren't any good either. I'm not sure what you mean about using ambient light sensors, how would they be used to detect touch? Anyone know how I could solve the sensor problem? I know (I think) that IR sensors with purely binary outputs (detected or not-detected only) exist - those would be simplest I guess but really I want analogue or 0 to 255 degrees of 'touch detection'.
Thanks again to everyone for your help.
