Dear Smith's!
I'm glad that you chose Poland for your vacation. I promise you that this will be a great time.
I know that you want to travel by car so you should start in Gdańsk. This is a one of the oldest cities in my country and it's placed close to seaside. There is coast with sandy, golden beach but you can find there also marvelous Old Town with lots of interesting monuments.
Later you need to visit south of Poland - drive there through Warsaw - this is a capital city, and through Kraków - this is the most beautiful polish city, famous for old castle with dragon and cute Old Market.