This year Brittany isn't the choice of destination...we will still be in France though.
If you do go to Carnac take Le Petit Train one evening...it gives a pleasant tour of Les Alignments...with a running commentary(listen for a couple of mistranslations) and baghad music..it is most relaxing.You can visit them again at your own leisure any time afterwards, for a more detailed inspection(you need to join a guided tour or get permission to get into some of them though).
If you visit the museum...please let me know your thoughts on the rock carving that Neo(the stone age mascot)is based on...see if you think similar to me.