I'm afraid I have no specific restaurant recommendations, but when we went to Sancerre several years ago, we first drove to Chavignol, where there are several wineries one can visit, bought several crottins de Chavignol, a baguette, some apples and a bottle of Sancerre. Then we drove to Sancerre itself where we found a nice park overlooking the Loire and had ourselves a great pique-nique. Of course, you don't have to stop in Chavignol to buy the same ingredients. Anyway, if you haven't been there, Sancerre is a gorgeous hilltop town, well worth visiting, though probably a 90-minute or so drive from where you're staying.
Chambord is awesome, the gold standard in wretched excess. And Blois is a great city. In addition to the chateau, you should try to see the Musee de l'Objet, which is off the beaten track but a lot of fun and well worth the 10-15 minute or so walk to get there. It's got a really intriguing collection of contemporary art and when we went there, it was like we had the whole museum to ourselves. There's also a museum of magic which you may or may not enjoy. I liked it and our kids loved it. The weird thing was that they had a magic performance and the guy who was there was from L.A., couldn't speak French and didn't even make an effort to, which was bizarre for us because I think we were the only English speakers in the crowd.
As I'm sure you know, you'll also be very close to Cheverny and basically within the Touraine appellation. I don't know how easy it is to visit wineries but I imagine your friend Joe could set you up to visit Clos de Tue-Boeuf, Clos Roche Blanche, etc...
Anyway, it sounds like you should have a great time.