Here's the information from the official site, as Mette pointed out:
Visit to Washington. The princes will take part in a conference that unites diplomatic, consulair and economic agents from Belgium in the US. They will attend a work meeting at the World Bank.
Prince Filip will also be present at a meeting of the board of direction of the king Boudewijn fund-USA, and at a remembrance ceremony for the 60th anniversary of the liberation.
Princess Mathilde will speak at a forum on micocredit at Georgetown University and will visit the Gallaudet University for deaf students.