How to power a 12v outdoor project with microprocessor?
Using AA batteries is not practical if you need an ampere for several hours. Based on your level of experience (I'm guessing) a small 12-volt sealed lead-acid battery sounds like a good choice. There's no point in trying to develop a high-efficiency regulator for the microcontroller, so just use a linear voltage regulator. Keep in mind that the voltage from a 12V battery actually ranges up to about 14V so make sure your LEDs can handle that. Small chargers for 12V batteries are available at your local huge box store or automotive supply.