I've been to Valencia and Annecy and loved both. They were very different, though. Annecy seemed much quieter, smaller, not as touristy, and with the lake instead of the ocean. Valencia seemed much larger, more to do, hotter, and with a traditional beach. Really depends on what you want. With small children though, Annecy is probably easier.

We were in Valencia in late July and my daughter stayed until late August. It was very, very hot. I loved Valencia but if I were staying for a month, particularly wanting to be outdoors, I would be planning for spring or fall. (I realize that won't work for you, though.)

Annecy sounds perfect!

Thanks! I honestly don’t think I could go wrong with any of these places.