>2) What kind of regulator should I use to provide my uC with 5 volts?

You need a 'boost' switching regulator. These are not trivial to deal with 
like linear regulators that reduce the voltage.

For your use I would strongly suggest that you use two cells, i.e. 3V 
nominal input - for a very good reason, batteries tend to be packed in pairs 
and not singularly. If size is a problem use two AAA cells instead of AA 
cells. This also has the advantage that you will achieve twice the mWh than 
a single cell will give.

For a suitable step up regulator I suggest you try this chip.
http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1042,P1958 and 
use the S8 package as this is the larger SO-8 package of the two options, 
and reasonably easy to handle. Pay careful attention to laying out the 
circuit board, the data sheet gives a good example of how to do it. By 
paying attention to detail the example circuit on the first page can be 
adapted to give 5V output with sufficient current capacity for your purpose.

If you want to investigate further the last page of the datasheet gives 
alternative possible devices from the same manufacturer. Just be careful 
which devices you wish to select, as some of them only come in packages 
designed for use in things like cell phones, and are not hobbyist friendly.


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