Hi, Richard.

I live about 30 minutes away from Fair Hill. It is a good sized Highland Games, with lots going on. I plan on attending, and hope to be competing on pipes, grade 4 senior.
Newark is more than tolls - it's the home of the University of Delaware, though a college town on its own may not be much of an attraction.

There are pubs to be found. I'd recommend the Deer Park Tavern (very relaxed) or Iron Hill Brewing (decidedly more grown-up) over Two Stones. I can't see any of these locations having a problem with kilts.

As for things to do or see, one of the biggest attractions is the ease of access to nearby cities. A couple of hours drive to NY or DC, and less to get to Baltimore and Philadelphia, depending on the length of your stay, you will be in a good location for many side trips.

For some closer attractions:
The duPont family is responsible for a lot of early industry in northern Delaware and South Eastern Pennsylvania. Some of their properties have been turned into museums:
Winterthur Hagley Longwood
If you like American History, the City of New Castle, DE is worth a visit for colonial architecture and scenery. A little farther will get you to Ft Delaware State Park, with its Revolutionary and Civil War history.