Renosterkop cottage was recently acquired by SanParks and very few people will have info on the cottage. The farm is indicated on the map and it might be possible to get a sea view from there, but it will not be close enough to walk down to the beach. I remember as a child in the 1960's our family used to camp at Struisbaai/ Agulhas and after Bredasdorp we would try to be the first to spot the sea. I think about 10 km before Struisbaai you can see the ocean.
The towns of Struisbaai and Agulhas already developed more than 50 years back as a holiday place for the farmers of the Overberg. Today there are plenty of accommodation available close to the beach at Struisbaai and rocky coast near the lighthouse.
The new accommodation available looks interesting and the best will be to contact the park to get more detail. The Lagoon house looks like the best option for a family to stay close to the beach and the Agulhas rest camp should be close to the sea when looking at the photos. The cottages on farms will be a bit further away.
Hope you enjoy your trip to the most southern point in Africa.