Thanks guys for the help. And thanks for the correction on the sensors' amps.
@fungus this is really helpful. Just to make it a little complicated, what IF I add a solenoid (12V 600 mAh) Lock-style Solenoid - 12VDC : ID 1512 : $14.95 : Adafruit Industries, Unique & fun DIY electronics and kits in the circuit. Would a 12V 3A enough to power everything? Thanks again for the help.
@Grumpy_Mike I already have 2 megas on hand ( i got 1 for free). I want the red led connected to the arduino pin as later on, I want to be able to blink it or do something with it. But the use of transistor will be very helpful if I abandoned the idea of blinking the red led. Also, I already got the 2 megas to communicate with the help of Master Writer/Slave Receiver example on this site.