How can I make a photo from my digital camera into a very small print?

I bought my wife a locket for Mother's Day and I want to put 2 pictures of my daughters face in it before I give it her. I have hundreds of great pictures of my daughter on my digital camera but I need to know how I can print those pictures from my digital camera out into actual photos that are very small so that they can fit into the locket. I have a printer at home and can buy photo paper I guess but more than likely I prefer to bring it to a local CVS or Walgreens photo lab. If I bring it to them I'm not sure if I need to do some prep work before or if they can do exactly what I need just from me bringing them my digital camera. Please help me with this, I suck at giving gifts and this time I can be a winner if I can just figure out how to do this. Thank you in advance and Happy Mother's Day to all of the mothers out there!