To me honest Janes blogs are probably the best source for itineraries. The Alignements are more accessible from October to March, although some bits were open when I was there late September last year. They never seem to open everything at the same time but you can do some wandering.
Whichever way my advice is always to get the Blue IGN 1:25000 maps Auray and Vannes sheets. All the stuff is marked by a pink star and the maps are pretty good quality.

Just be aware that, even if the main Alignements are closed off, there is tonnes of really great stuff to see, and the lesser known sites are very rewarding (if you can find Kerlescan Nord you get a medal, or should at least!)

Off the beaten track Erdeven, Crucuno dolmen and rectangle, Coet Er Bei, Le Bono, Mane er Hroeuk, Mane Rutuel, Les Pierres Plats, Le Moustor and quite a few others are musts.

Keep watching ebay etc for Aubrey Burl's Megalithic Brittany. It's a bit out of date now but is still the best guide there is