Are you going to take the I-95 or the Eastern Shore route? Both go through Delaware. What would you like to see?
I-95: Havre-de-Grace, Baltimore, Alexandria, the US Marine Museum, Williamsburg.
Eastern Shore: Chincoteague/Assateague, any number of cute, little towns.

Even though I have absolutely no idea of what kind of sightseeing you are interested in, I'll mention this place as a possibility

http://www.nps.gov/asis/index.htm

Of course, if beaches or unusual wildlife are of no interest to you, then feel free to just keep driving.

The Smyrna Diner for sure and a great meal; right off the Del 1 Turnpike

Good to know, Dukey. I'm always looking for "real" food along 95.

Thanks for the input! We would go the Eastern Shore route.

Could take 95 to Elkton, take 213 South through Chestertown ant to Route 50. Take 50 East through Easton, Cambridge and to Salisbury. 13 South from there to the big Chesapeake Bay Bridge.

Ocean City, MD, if that is your kind of thing. It is likely to be VERY congested in August, however.

I highly recommend Chincoteague and Assateague National Seashore if you like beaches, wild ponies, etc. We vacationed there several times when our daughters were younger & have very fond memories. We are from MA, & especially like Chincoteague/Assateague because it is quieter than Cape Cod. There are good seafood restaurants, mini golf, etc.

Wilmington, DE has a cozy city environment. It is just 45 minutes away from Philadelphia. It has a very flavorful Jamaican eatery in the heart of its downtown. Any local can get you there.

If you are into vegetarian eating, try Soul Vegetarian in DC. It is soul food but mostly vegan. Delicious and nutritious food.

I agree with Kwoo's remarks and going the Bay Bridge.