Can decoupling capacitors be doubled up? Xbee + VR both have them
This all depends on the frequency of current draw of the device on the line, the frequency response of the capacitors used, their ESR, parasitic inductance of traces joining capacitors and loads and actual physical layout. The purpose of decoupling capacitors is to provide a local power source for the load and keep the voltage rail clean (these two are different ways of saying the same thing, effectively).

Placing individual capacitors physically close to the IC they are supposed to be decoupling minimises trace inductance and hence maximises their suitability for purpose - so the fact that you have three capacitors all on the same line adding up to ~2uF doesn't mean that you could replace the three with one 2uF capacitor and have it act exactly the same - each is connected to the next via a small resistor and a small inductor representing the impedance of the copper between the two.

How much ripple can you tolerate on the power rails? If you know this you can measure existing ripple under worst-case conditions, remove a capacitor of your choice and repeat the measurement. If that takes you out of specification - put it back! Don't forget that you will need to repeat this measurement at each of the ICs you have with the shortest possible ground lead for the 'scope. You should be able to get hold of some ground springs like the one shown below to help this. If you use the standard lead you get with the scope, you will be measuring with its inductance in place too which will make your measurements pretty much meaningless.



So what should you do? Well, if it were me I would leave the existing caps in. They cost almost nothing and aren't likely harming anything. If you really need to remove one or all, then do it using the approach I have described.