Wiring 2 gang light switches

If I understand your layout, you could wire it like this:

Chaining to all four lights like this requires the use of 12/3 cable for the first two sections, but if you want to follow Tester101's suggestion and add the extra conductor to the fan circuit for possible future use, you're going to buy some 12/3 anyway.

EDIT: Carl Witthoft is correct, the bathroom should be protected by a GFCI. I have altered my diagram to show a GFCI outlet with downstream protection.

I believe you are correct in assuming that one switch controlled the fan and one controlled the lights originally.

My guess is that the wiring at the fan just has both the red and black wires connected to the line side of the wireless receiver, which would let either switch turn the fan/light on.

I would look at the wiring at the fan to confirm this. If I am correct, then yes, you should be able to disconnect the red wire. I would disconnect it from the fan and from the switch in the box and cap both ends.