500 ma for 100 ma requirement?
The power supply is rated at 12Vdc and can supply up to 500mA. This means it will not be overloaded with a 100mA load. That's the theory anyway but i will add that it is totally worth measuring the 12VDC output with a meter first to 

a) Make sure you know the polarity i.e. which line is positive and

b) Ensure it doesn't produce 18V on light loads dropping down to 12V on full load.

Don't be surprised at (b) - I've seen it