The workshop immediately follows the HEPiX, so if you are attending (parts of) that, it makes sense to just hang on to your room and stay in one of the HEPiX hotels.
Additional hotels both close to Nikhef (Science Park) and in the direction of the city centre are listed on the Nikhef accomodation map.
You should make your own booking at these hotels, eithe rdirectly or through your favourite agency. The Nikhef secretariat will not book hotels on your behalf.