Help with designing an LED circuit
The first thing I would do if I were you is consider using a different power supply. 8xAA batteries is alright, but your LEDs are going to drain them sure quick. You mention the battery capacity is 2650mAh. This means it can power a circuit of 2650mA for 1 hour, or 1325mA for 2 hours etc etc. Your circuit is 1.75A which means assuming perfect batteries and perfect conditions with no loss of power during discharge, you still only get 1.5h of battery life. This seems like a complete waste of 8 batteries. Hence, I would say change your power supply.

If you insist on using these, consider lowering your current. Get some low current LEDs or limit these ones to around 5 or 10mA (if that is bright enough) to lengthen the time your circuit works. You will also be needing a voltage regulator. Your batteries are going to drain, and as the voltage gets lower, your LEDs will dim. You will need a regulator to stabilise the voltage.

Now to tackle making them blink. If you want to use the transistor/capacitor way of doing things, google astable multivibrator circuit. Read up on how they work and understand it before building it.