If you have 2 Arduino Megas then that's enough Arduino pins.
The main problem will be your 12V supply. Regulating 12V down to 5V is going to generate a lot of heat (+wastage). You can use a more efficient switching DC converter (eg. this) but it's still quite a lot of amps.
How many amps?
Your sensors don't use 25mA, they can switch up to 25mA through their transistor. For themselves they use 4.4mA (typical) according to the datasheet.
So...each LED+sensor pair needs about 25mA. 52 of those gives 1.3 amps. Add in a couple of Arduino Megas, call it 1.5A total. You should probably get something capable of at least 2.5A to keep things cool/reliable.
Power?
5V@2.5A is 12.5W of power needed in theory.
12V@1.0A (your power supply) is 12W (which converts to 5V@2.4A if we can convert with 100% efficiency).
So...your power supply is just about up to the job, if you get an efficient converter.
That polulo converter claims 90% efficiency which translates to 2.1 amps maximum output using your power supply. We need 1.5A so your power supply will running at about 75% load, ie. it will probably get quite hot. It's up to you, but ... I wouldn't wouldn't do it if it's a cheapo power supply.
You can get a 5V, 3A power supply for less than the cost of that converter. To me that seems a better option.