I would like to suggest Kiawah for SC and of course dinner/lunch date with em:)
I know it's nothing crazy but the 5k color run is September 28th,14 and it would cross D.C. off your list ;)
I've always thought about doing the vancouver Washington / vancouver BC marathon duo... i don't know why it just seems cool.
A fun tri (olympic or half) is SuperiorMan in Duluth, MN. The swim starts by jumping off a ship in the harbor. We're doing this one for the first time in August 2016.