While one may not think of Lancaster, PA, as a place to go on a family holiday, it has a plethora of family-friendly and affordable activities for kiddos. Make sure you stop at the Turkey Hill Experience, where visitors make their own ice cream flavours (there are also free samples of ice cream available as you tour). Then head to the wolf sanctuary, ride mini horses, take an Amish buggy ride, get a rush at Dutch Wonderland amusement park, and grab a piece of pie from Dutch Haven.
Note: Sesame Place and Hershey Park aren't that far, either, and may be worth a day trip!