I personally use and recommend Linux Mint: http://www.linuxmint.com/
Mint can be installed in about 1 hour following the instructions on their site if you have a strong DIY ethic. You will need a blank USB thumb drive (since the Acer doesn't have a CD drive). I always recommend to test-drive in "Live" mode before installing, to verify that your hardware is supported (and that you actually like it).
Linpus and Mint are two of the hundreds of distributions or "distros" you can compare at: http://www.distrowatch.com
Maybe installing Linux together can be an educational co-project with your daughter, then you don't have to panic to get it done Xmas eve.