It's probably on the far side of your travel limit, but the entire Traverse County/Sleeping Bear Dunes area of Michigan is gorgeous and it really feels much more of a getaway than it sounds because there are such lovely resort towns. Manistee is very pretty and close to the Sleeping Bear Dunes National Lakeshore. Traverse City and the Leelenau Peninsula, you will fall in love with. Last summer we rented a cottage in Boyne City (other side of Traverse, near Petoskey) - beautiful (warm!) swimming beaches on Lake Charlevoix, more fabulous, not-too-crowded state parks, and the rental prices in that area were really reasonable. Plus, there were several adorable towns with great food and antique stores within close driving distance of our cottage.