What about Michigan? We did a road trip there once. Started at Traverse City (toured the lighthouse & foghorn buildings at Northport, visited the music museum at Acme, drove the scenic route up and around the lake), that took us on up towards Mackinaw City and Mackinaw Island. Rode the ferry over to the island. There's some sort of fort there also. Then we stayed in Frankenmuth, a little german town, see
www.bavarianinn.com That was a neat little town. The hotel had quite a few indoor pools/hottubs and even miniature golf inside. There were lots of little shops and a huge Christmas store (Bronners). We even got some strolling polka music at our table.
Williamsburg and Monticello were also interesting. We enjoyed them, however, I'm not sure kids would appreciate it.
What about Victoria BC? We visited there once for a day on a cruise up the west coast. Loved it! We had tea at the Fairmont Empress, toured Craig Darroch Castle, got candy at Rogers Chocolates, rode around town on a double decker bus, and there's also Butchhart Gardens to see. We are hoping to return there. My plan is to fly into Seattle and ride the ferry (Clipper) over to Victoria. We want to do a Whale Watching excursion this time. And if possible we may stay a night or two in Seattle and see the sights there.
I might add for those who suggested Niagara Falls. We went in June this year. It was a frigid 53 degrees. We stayed 2 nights on the 26th floor of Embassy Suites (Canada Side). The view was fabulous. The prices for everything were outrageous. We were glad we only were staying 2 nights as we did not find a lot to do there. There were two casinos, but we aren't casino people. The Clifton Hill area was a little bit creepy to me, sort of like a side show area with wax museums etc. It might have been better if we would have had our car and could have driven on north and seen a bit more of Canada. I would have loved to have seen Prince Edward Island.
What about an Alaskan cruise? We cannot wait to do that trip some year. Lots of adventure out there. Whale watching, scenic flights, etc.
Have fun, whereever you decide to go.