IR proximity sensor - questions


I'm planning to build an interactive LED-table based on iTead Studio's Colorduino. Instead of the RGB matrix module, I plan to connect common anode Superflux Piranha RGB LEDs.
In addition, I plan to use an 8x8 matrix of IR proximity sensors for interactivity.

The Arduino part is no problem. I have done a few smaller projects and I think I am reasonable fluent in Arduino C.
My problem is basic electronics. My last practical experience with basic electronics was about 22 years ago during school time.

What I wanna do is design small PCBs which hold the Piranha LED plus the IR sensor and have those PCBs made.

Now, the problem... How should I design the IR proximity sensor? The table should have a plate made of frosted or milk-glass.
How many IR emitters should I use for each sensor and how would I build it. I know how to design a basic detector with a photodiode but I'm uncertain about resistor values and in the net I have also seen examples using multiple photodiodes in some kind of voltage divider circuit.

That's what I have so far:

Next thing I'm uncertain of if the method. I was originally thinking of using analog ins (on a Mega2560), so I have also some distance value to tinker with in the code but I wonder if this makes sense at all - does this work through milk-glass?

I'd appreciate any comments or insights on those 2 issues.