I would highly recommend Stadsherstel Rotterdam - we stayed in the Karot Studio on the first floor and this space was perfect for us.
The apartment was spacious, impeccably clean and the view out to the lake and gardens was so relaxing. So beautiful to sit and watch the sunset each night and watch the water birds come up to the garden of a morning. We didn't want to leave!
The windmill next door is very interesting and my son and I had a tour when they were open.
The location is excellent if you want to visit Rotterdam but not be in the centre - the park is beautiful with multiple playgrounds, a little farm and some excellent restaurants and cafes in walking distance. If you are visiting with young children this is an excellent location to base yourselves.
Communication was fantastic - very easy to check in and out and Ericia was very responsive.