The Locket - Tales From Avenrand, #1

A young widow, Lacy, discovers magic in her grandmother's locket and uses it to go back in time to try to save her husband and keep her family whole. But when the locket accidentally takes her and her daughters to another dimension, she discovers she can't completely control the magic. Though the enchanted land of Avenrand is full of wonder, a darker presence lurks in the shadows, threatening all who travel its realm.
Now Lacy must find her inner strength to lead her family home or lose her daughters forever.