Gace I'm not so sure about because it is in very easy striking distance of the motorway. Vimoutiers you will not need to book, although the best piches go by the late afternoon.
I don't know how to put images onto this forum but I have put some photographs of the campsite at www.wyburns.com/vimoutiers.htm
Vimoutiers is well worth the extra 20 minutes drive.
But don't tell too many people!