creating a small 8 channel transitter and receiver? (preferrably RF, not IR)

So I have a project in mind... but have never worked with any kind of transmitter or receiver. I'd like to take an NES controller and make it wireless. I'm thinking I'll need a small lion battery (14500 li-ion), power switch (spst switch), DC jack for charging (4.2vdc directly into controller), voltage/current regulator (lm317 ?), and RF transmitter/receiver (no idea ???)

transmitter requirements: needs to be 8 channel (up, down, left, right, A, B, Start, Select) and have the ability to transmit/receive multiple signals simultaneously. The transmitter also needs to be small/minimal... after the battery, switch & charging jack there wont be alot of room left in the controller. The receiver can be much larger because there's alot of room in an NES. The receiver can be spliced into the backside of the original NES controller port (so a wired controller can still be used).

Any suggestions on RF parts or circuit diagrams? I've tried Googling for some stuff, but I'm woefully inept when it comes to wireless circuits. Is it more difficult than I'm imagining... have an 8 channel transmitter and an 8 channel receiver that simply activates a transistor/relay to ground the original NES controller circuits??

What kind of "lag" time would I be looking at?

A few more questions pop into mind as I browse around the internet for info...
What kind of power do I want? Transmission will be through open air about 15-20ft maximum (playing videogames).
What frequencies work best/safest? Obviously, interference causing Mario to commit suicide is undesired.