xn1ch1:
25 x 3mm 5v 20 mA LEDs
2 x sets of IR led and phototransistor 25mA...will the Arduino handle all of that?
Probably. The UNO's regulator is a 7805, I believe ncp1117st50t3g, which should be able to provide up to 1A in theory, although better to stay well away from the limit. If all 25 LEDs and the 2 IR LEDs are all on at once, this would dominate the current needs and be 500~600mA. The other components will probably need a few mA each.
xn1ch1:
could I use a second 5v regulator off the VIN to power the TLCs leaving the Arduino to handle the rest.
Better to have a separate connection to the DC supply, to avoid overloading the UNO's PCB track.
xn1ch1:
If so, I've found a tiny breakout that has a V+ and gnd for both in and out, where does the ground in come from?
From the -ve connection on the DC power supply. All grounds should be connected together in your project.
Sounds like a very "different" alarm clock. What to the gyros and IR leds do?
Paul