Multilayer Ceramic Capacitors are not normally used when you want a capacitor with low ESR, that's why they don't put it in the data sheet. You will find in in the sheets of polarised capacitors. By and large if it isn't in the data sheet they are not proud of it.
The opposite is true. MLCC's have extremely low ESR (see this presentation
for example), lower than that of tantalum, and often too low for LDO's that expect a minimum ESR for loop stability.
The RXJ010M2ABK-0511P is definitely overkill for this application (100V??) but its impedance is fine -- 0.16 ohms at room temperature (I'm not sure where you got the 7 ohms number from).
The Gadget Shield
: accelerometer, RGB LED, IR transmit/receive, speaker, microphone, light sensor, potentiometer, pushbuttons